I'll get to the point. Martials are generally boring to play in combat, and get outclasses by casters by late game. You know it. I know it. Lets not arguing too much about it. But one martial class (subclass, actually) is the shining exception to this. The Battle Master is the example on how to take combat from, "I attack, roll damage", and make it interesting. So how do we alter this in 5e without a complete overhaul of the system in place? Well, easy enough. You give all martial classes access to Battle Master Maneuvers. The system is already there, the maneuvers already exist, they have been tested and people really like using them. What could possibly be the objection to this? Sure, it might not actually fix the martial - caster imbalance, but it does make playing a martial more fun in the long run, which is far more important.

     Okay, so I get this sort of kicks the ACTUAL Battle Master's pretty hard to the curb if improperly handled. Not only that, how do you give these things to martials without just letting casters multiclass and dip into a martial class just to get them (something people already tend to do with Fighter as is, and will probably continue to do so despite this homebrew)? Easy enough, we just continue to use a system already in place that sort of works in a similar fashion, by tying them to ASI/Feat tiers. This also further rewards pure classes a bit more, since multiclassing often will lose a player out from an ASI/Feat anyways (and with this, also an additional maneuver+superiority die). If you're a couple steps ahead of me, you'll probably guess correctly that I'm also going to utilize the criminally sought after (but never good enough to actually get chosen) Martial Adept feat as the remedy for this.

     Great. So who gets to benefit from these maneuvers? Barbarians, Fighters, Monks, Rangers, & Rogues. What, no Paladins? Correct, no Paladins. They get smites in place of maneuvers while also being one of the most powerful classes in the game inside AND outside of combat, being able to achieve a ton on all angles/aspects of the game. They don't need this.

     So here's the general rule of thumb: Anytime a martial class (listed above) would benefit from an ASI/Feat in that class, they also get to benefit from the Martial Adept feat, except they are only permitted ONE (1) maneuver option from the Battle Master list.

     But why only one? The reason for this is fairly obvious; this homebrew is a straight buff to the classes it applies to, and it's smart to not go overboard. This also still gives merit to an actual dip in the Martial Adept feat (but lets be real, no one chose it before, no one will choose it now), and it is the perfect number to benefit ACTUAL Battle Masters by completing their known maneuver list without exceeding the total number of them known (9 from the BM subclass, 7 from their ASI tier, with 16 total known from 16 maneuvers). This also helps non-BM fighters still get the most benefit from the homebrew by having the most ASI options (which, if we went with the full benefit from Martial Adept, would end up getting 14 maneuvers total, rendering the BM sublcass less ideal, which is not the point to this homebrew). 

     So what do you think? I know I'm going to try this the next group I get, but would like to hear some feedback on possible issues it might cause (and hopefully without invoking too much wrath from the local Paladins).

This is a really cool idea! I'm familiar with a few of the Battle Master Maneuvers (we have a lvl 6 BM in our current group) but I should probably look up the full list....

That said, are there any maneuvers that synergize too well with any of the above classes? (Sort of like the "bard test" for homebrew spells... if a bard will always take it with Magical Secrets, it's too powerful). The most powerful interaction that comes to mind for me is slapping Riposte on a Rogue for an easier shot at two Sneak Attacks per round - I don't see why any rogue with this homebrew idea wouldn't immediately pick Riposte as their first option.

Just my thought. :)

Solid point with the Riposte on Rogue (and the sort of interaction I never thought of that could end up being an issue). It is a powerful combo, but only gets 1 use of maneuvers at lvl4, 2 at lvl8, and 3 at lvl10 per short rest. Could change the "free" maneuvers only recharge on Long Rests, but taking the Martial Adept feat gets the bonus ability to reset maneuvers on short rests as well. (Helps make the feat more useful in conjunction with these rules). 

Thanks for the insight.

Monks really suffer from a lack of maneuvers - especially when martial arts is all about being able to use various kinds of maneuvers for any given situation.  There are a lot of great martial arts maneuvers that could be used to build a fighting style for a monk: flying kick, roundhouse kick, reverse roundhouse kick, side kick, butterfly kick, various joint locks, vital point attacks, etc.  Many of these maneuvers already have cool names like "black dragon shakes its tail" (reverse roundhouse), "grasp sparrow's tail," that would add a lot of flavor!

There is a ttrpg that first  got me interested in ttrpgs before I played dnd called perilous ventures that only uses d6. Now then one great thing about it was how open and customizable it was. In it every class gets some sort of maneuvers that they can use to spice up combat but they also have maneuver points (6) that are limited but regenerate over time (1 per round(can be changed to 2 to fit better)). If you scroll down to the thief and warrior class (only 4 classes) you'll be able to see their maneuvers and with a bit of rework to make it fit 5e (since they are majour parts of how the characters work in game) you could make this idea a reality. Or maybe just keep the points but replace the maneuvers with battlemaster ones with how many points you spend replacing the battlemaster dice.

So just to clarify, you mean that the martial classes you list get the Martial Adapt feat for free every time they get an ASI?  The first would be at level 4, which world prevent any multiclass dips just to get it.  And Fighters would get more because they get more ASIs.

Do I understand that correctly?

If so, then it sounds acceptable.  

I think Maneuvers should stay a Fighter exclusive thing, but that a limited version of it should Hana base class feature for Fighters.

Quote from IIIHUSKIII >>

 So here's the general rule of thumb: Anytime a martial class (listed above) would benefit from an ASI/Feat in that class, they also get to benefit from the Martial Adept feat, except they are only permitted ONE (1) maneuver option from the Battle Master list.

I dunno. Maneuvers without any options to avoid them might be complicated for some people. Especially for people who actively picked out a class that was "simpler" and easier to play, such as Fighter. So I like your idea, but why give them a maneuver and a feat or ASI? Can't you just let people pick between the two? That would allow players who want complexity to have lots of it if they want, and players who like simplicity wouldn't have to deal with that. Superiority might end up feeling somewhat bland if you got it every time you played a martial. But this is an excellent idea overall, good job!