This is my personal wishlist as a long time DM (playing since 1st AD&D in the 80s).

• Full backward compatibility. Can use the new 50th anniversary edition stuff with the old 5e stuff. 
• Would love to see higher CR monsters (tier 3 and tier 4) more hard-hitting and challenging;
• On a related note, would like some hit points cap for player characters, like some earlier editions...
• Adjust / tweak / balance some of the spells at are either normally considered too weak for their level, or too strong; (plenty of YouTube videos out there from well-known people in the community that already underline many of these)... For example, I like Treantmonk's suggestion of the Shield spell giving a +3 bonus (instead of +5) at 1st level, and increasing by +1 when upcasting. I would also bump levels of spells such as Banishment (used to be a 7th level spell in earlier editions...)
• Similarly, adjust / balance feats and some of the class features... For example, imo eldritch blast should be an exclusive warlock feature spell, and feats such as Sharpshooter, Greatweapon Master and the like should have higher level requirements -- or bonuses to damage that scale according to a character's proficiency bonus.
• Multiclassing rules that discourage 1 level dips.
• Make combat more threatening (i.e. challenging and fun) by increasing the possibility of character death, increasing game tension. Having some kind of Staggered condition when you fall at 0 hp.
• Fewer damage and condition immunities, especially for characters for tiers 1-3 (although fewer creatures immune to poison would be nice too...) Immunities should be rare(r). Most low, mid-level spells and features that offer character immunities or outright end conditions should offer resistance or advantage on saves against a given condition instead. Looking at you, Heroes' Feast, Twilight Domain cleric...
• Make the differences between the various damage type matter more. For example, giving each damage type a "critical" secondary effect on a critical hit, or its own lingering injury table... ; 
• Perhaps introduce some sort of dual-concentration rule, that would allow *some* concentration spells or effects to be used simultaneously. If you lose concentration, you lose both effects. That would be useful to balance some class features and make some utility spells more used at the table.
• Make Strength score more useful in various ways.
• Balance skills; make them all worthwhile. Medicine and other knowledge skills should be as useful, fun, and appealing as Athletics, Perception, or Stealth. 
• Speaking of Athletics, a lot more fighting-type monsters should be proficient in the Athletics skill, for combat purposes (grapple, shove contests)... 
• Adjust the rarity of some magic items. Some uncommon items in the game should probably be rare or very rare. (The winged boots come to mind...)
• More elaborated theater of the mind / narrative combat rules. Especially rules regarding speed, movement, opportunity attacks. A fast-moving monk, that gets a movement advantage on a grid, should get some sort of benefit when using narrative combat (a small boost to AC?)

That's it for now. In short, a grittier, more challenging D&D iteration... I understand game design is hard work, especially when you're trying to please as many DMs and players as possible, so thanks in advance.

I mostly just want them to fix their weird wording. Like the "weapon attacks vs attacks with weapons" thing. All that kinda stuff. Basically you can search for the most common rules questions and fix them so they're unambiguous. And I imagine they will.

Rebalancing classes, feats, and magic items would be appreciated. There are some real stinkers, and some obvious best choices.

My own personal opinions get pretty specific so it's hardly worth mentioning them. Stuff like, I'd like to see the return of true Vancian magicians. Stuff that'll never happen, and for good reason.

- Multiclassing removal, more "feat focusing" class customization(more feat in general and especially feat with high requirements).

- ASI\Feat separation.

- Abilities rebalance(like one example;  make Str more useful and Cha weaker by doing Intimidation Str-based).

- More variety in weapons.

Fix. The. Falling. Damage. System.  Please. 

And Thank you.  :)

1. I want feats to be more available to players. Rather than having to choose between an ASI or a feat, let me have a source of feats that don't feel like a massive compromise. They can still have the choice for people who don't want an ASI, but also have criteria for granting feats as well.
2. More interesting feats for casters. They're coming, but locked to these random adventure books. With a new PHB, I'd like them included in the PHB too.
3. I'd like to reduce the impact of ASIs, specifically on character abilities. I'm absolutely fine with the whole to hit/damage bonuses,.but I really don't like the idea that how many spells I can prepare is based on the modifier, and things like that. Missing a few extra attacks is fine, but to objectively be a worse Wizard because I have a restricted availability of spells really sucks. Perhaps have it based more on PB or just level or something.
4. Move away from the builds a bit. I'm not a fan of the idea that generally speaking, you design your build, then you let it loose on the world. Mechanically speaking, your agency is used at character creation and levelling up, then you have an optimal approach to problems according to the build which you follow or not. I prefer the feel of STA where you have a pool of dice that you can earn and spend on tasks. You have to decide what to "try hard" on by spending a ton of dice, what to gamble that you can get by on fewer dice and conserve them. The system doesn't have to be copied, but I like the fact that you have choices beyond "this is the optimal path that my character is built for, do I take it or not?" and instead allows agency to be invested in the tasks themselves - which may not even have an objectively correct approach. Yeah, ok, that's more a 6e thing than a 2024e thing.
5.  Fix wording to be more intuitive. Better quality control on that too. I really shouldn't need be checking multiple sources to understand how things work. Just get an idiot in to try and misinterpret what's being said and fix it until it's clear.
6. More classes please. I'm sure there are a couple more ideas big enough to merit a class.
7. Better quality control on adventures please. I'm tired of adventures offering multiple methods of accessing a dungeon, then describing the dungeon from a fixed route, so it causes a headache for the DM as they have to interpret what's being said and reword it to match what direction the party is actually coming from. Or at the very least, if they do insist on that presumed.direction, at least make it match up with the most obvious method of entry. In LMoP, they even shoved the "secret entrance" down the party's throat while hiding the main entrance, then proceeded to describe every room as if they'd come in to through the main entrance. Gah.
8. More Elves? Just kidding.
9. Some in depth lore books to help us newbies learn more about the settings, the history, how the cultures work etc. Not all of us have been here since 1e and have everything memorised.

1. Prestige Classes

2. Feats should be more available

3.  More Backgrounds

4. Skill Points

5. More Epic Level options.

6. Magic Item pricing and more availability.

7. More player customization.

7. Opportunity Attacks.

8. More weapon choices.

9. Thri-kreen as a playable race.

10. More Krynn and Eberron.

11. Critical Fails and better critical rules.

Quote from CubedTundra >>

 

9. Thri-kreen as a playable race. 

 Spelljammer campaign setting ;)

Other than that:

1) More precise rules wording

2) Better design of solo/legendary monsters, that are a real challange for larger groups

3) Better balanced spells per spell level

4) Combat Feats / Non-Combat Feats from seperate sources and decoupled from ASI, plus balancing of feats

5) rework of short rests / long rests / natural healing

I, like everyone else want them to rebalance the classes and subclasses against each other. And like everyone else I want them to plug up all the holes in their verbiage. As for more specific wishes:

1. I wish Eldritch Blast was a Warlock feature instead of a spell.
2. I wish they would raise the top end on Strength based weapons from 1d12/2d6 to 2d8/4d4 instead. That would make Strength a more important ability, and it would allow for a few more weapons to fit into the list to add a little variety to the mix.
3. I wish that the “using skills with different abilities” optional rule was the standard rule for skills.
4. I wish that they would keep both fixed and floating racial ASIs as side-by-side options the same way we have three options for how to generate stats for our PCs, that way everyone gets what they want and we can all stop arguing over it.
5. I wish that Artificers will be included in the PHB and new SRD as an “official” base class so they can publish subclasses for it more easily.
6. I wish they would make called shots with a -5/+10 a standard rule (only change -5 to disadvantage) so that GWM & SS stop being auto-include god feats.
7. I wish they would change Long Rests so that whenever you take one you get back all of your Hit Dice but only half of your HP to encourage more Short Rests.
8. More cowbell.

I wish for an optional rule that all Level 1 start with Commoner stats with an adjusted attribute progression. I would say, "House Rule" it, but apparently according to far too many people, if it's not printed, it can't be used and, if it's printed, it must be used.

I wish they would push harder for people tweaking the system to their liking for their campaign and their table. It's like people just aren't getting it that they can do that already.

Quote from CubedTundra >>

1. Prestige Classes

2. Feats should be more available

3.  More Backgrounds

4. Skill Points

5. More Epic Level options.

6. Magic Item pricing and more availability.

7. More player customization.

7. Opportunity Attacks.

8. More weapon choices.

9. Thri-kreen as a playable race.

10. More Krynn and Eberron.

11. Critical Fails and better critical rules.

 

 Yes!

Quote from IamSposta >>

I, like everyone else want them to rebalance the classes and subclasses against each other. And like everyone else I want them to plug up all the holes in their verbiage. As for more specific wishes:

1. I wish Eldritch Blast was a Warlock feature instead of a spell.
2. I wish they would raise the top end on Strength based weapons from 1d12/2d6 to 2d8/4d4 instead. That would make Strength a more important ability, and it would allow for a few more weapons to fit into the list to add a little variety to the mix.
3. I wish that the “using skills with different abilities” optional rule was the standard rule for skills.
4. I wish that they would keep both fixed and floating racial ASIs as side-by-side options the same way we have three options for how to generate stats for our PCs, that way everyone gets what they want and we can all stop arguing over it.
5. I wish that Artificers will be included in the PHB and new SRD as an “official” base class so they can publish subclasses for it more easily.
6. I wish they would make called shots with a -5/+10 a standard rule (only change -5 to disadvantage) so that GWM & SS stop being auto-include god feats.
7. I wish they would change Long Rests so that whenever you take one you get back all of your Hit Dice but only half of your HP to encourage more Short Rests.
8. More cowbell.

1.  More Cowbell!
2. The first tier has more Short Rest resets for every class except for Warlock and Monk.
3. They focus more on proficiency bonus than an arbitrary number, or ability score.
4. Condense the weapons list, then expand it in a more logical way. Bob Worldbuilder is doing a great series on it. I only agree with half of his design, but it's better than what's in the PHB.
5. Give tools more utility.
6. Change the default world to Mystara (for adventurs like, "The boat one" and "the jungle one"), and use Dragonlance for unique Stories... and give both Planescape and Spelljammer a bit more love. Heck, each game gives better focus to the other two pillars of the game and should get a release each year or two.

1. Rebalance encounter design around a 1-3 encounter day, not a 6-8.
2. Get rid of the adjusted xp system; it just confuses new DMs. Either change xp values so it's not necessary (requires changing the level-up tables so seems unlikely, but it's possible) or use a secondary point score.
3. Balance fixes would be nice, though big job.
4. More interesting monsters, either by default, or by adding a template of some sort.

Quote from Pantagruel666 >>

1. Rebalance encounter design around a 1-3 encounter day, not a 6-8.

 That really would be great. A variant rule for dungeon crawls, perhaps... Or some rules for in-universe limitations on dungeon exploration, like a magic ward that makes it impossible to fully recover HP on a rest within a dungeon, or a magic shrine that can recover certain expended resources. That way you can still run longer adventuring days without even having to adjust the rules. (I still think it's crazy how there's all these gods in D&D, and the only person who cares at all, is the Cleric, and even the Cleric only cares about one of them.)

But yeah. A system that's designed around shorter days. I do wonder though. It would basically nerf casters (fewer spell slots) and buff martials (no equivalent resource = no loss). Is the world ready for such madness?!

Please; in the name of King Midas: FIX the economy!  I know it only bothers obcessive "logical world" sorts like me: but honestly a lot of the prices in D&D make ZERO sense.

Besides that though: to eachoe others:

- Fixing the balance issues

- More player customization

- More feat/segregating feats and ASI systems

- More utility for tools/crafting

• A completely new, non-medieval-european base setting.
• Restore magic item levels and get rid of the rarity system.

This is fun, but I think expectations are way high here. I'm expecting something more along the lines of a basic reprint of the PHB that updates the base content to the new design patterns, in the same way MoM updated older monsters and the non-PHB races. They're tightening up this ship, not building a new one.

I think maybe some better worded rules is possible, but I'm really not holding my breath for a completely revamped ruleset or anything else on the level of 90% of the suggestions here. Best I hope to dare for is baking in the concept of Class Feature Variants to give us more options in future books.

Quote from ChoirOfFire >>

But yeah. A system that's designed around shorter days. I do wonder though. It would basically nerf casters (fewer spell slots) and buff martials (no equivalent resource = no loss). Is the world ready for such madness?!

Oh, I wasn't assuming a change in number of spell slots. Just a change in encounter guidelines. If the adjusted xp system wasn't such a mess you could do it by just doubling all the budgets.

Ah, just you wait until they extend the "proficiency bonus uses per long rest" concept to spell slots for Wizards. ;P

Quote from ChoirOfFire >>

Ah, just you wait until they extend the "proficiency bonus uses per long rest" concept to spell slots for Wizards. ;P

 
Saints in heaven preserve us.

Lots of stuff I've forgotten, so I'll keep adding to this list.

- Backgrounds get extended and made more impactful.

- Feats and ASIs disconnected from each other, and moved to character level rather than class level.

- Invocation/Infusion like options for all classes. 

- More classes. I'd like to see a psion, warlord, and swordmage get added as official classes. Maybe add bloodhunter, though it's a bit setting specific like artificer and also seems to have a bit too much 3.5e design to it. Still really fun to play though.

- Bring back the playtest sorcerer.

- As racial ASI's are all the same, just delete them or move that into the ability scores generation section of character creation.

- Manoeuvres for all martials. Some will be usable by multiple classes. Others unique to a single martial.

- Allow warlocks to either customise their eldritch blast a lot, giving it different abilities or effects. Or allow invocations to apply to other damage cantrips. I like warlocks being a cantrip spammer. But at least let them mix up what they can do with it.

- Make strength not useless.

- Make enemies have more interesting abilities, rather than being HP stacks. Bring back the bloodied condition and abilities.