So I had this idea for a pokemon campaign that doesnt involve being able to catch the pokemon, as thatd be a logistical balance nightmare. Instead, the idea is to meld a normal fantasy world and pokemon worlds together, with pokemon being able to bestow a specific kind of charm upon those who befriend them(charms being found in the DMG). Each Pokemon's statblock would contain the following action-
Imbue The Pokemon targets a friendly creature it can touch, and chooses one of its types. That creature gains the charm of that typing. When this ability is used, it cannot be used again for a week.
Then the actual charm text:
Charm of Imbued [Pokemon type] When you make an attack or cast a spell that deals damage, you may ignore the damage type, and instead use the damage type of this charm. If one of the creatures taking damage is a pokemon, it instead takes damage based on its pokemon types compared to this charms type instead of its normal resistances or immunities. This charm can be used once before vanishing from you.

Basically, each pokemon type will be assigned a damage type based on what it is to use damage standard DnD creatures, but types will deal damage to pokemon using their pokemon type immunities, resistance, and weaknesses. Players will have limited use of the pokemon types, though, so it will be strategic when to replace damage. For pokemon types to normal damage types, I think the following should work fairly well:

 Pokemons statblocks will just have normal DnD damage types in their attacks to make things simple. Any thoughts, advice, or ideas to improve this concept? 

It sounds like a fun and simple to implement idea, assuming I'm understanding it correctly.  Does it basically mean that each pokemon you have befriended can let you change a damage type on one attack once a week?  If so, it's certainly not overpowered.  It's unfortunate that DnD doesn't have enough damage types to fully implement the idea.  A lot of them seem to just ťurn into B/P/S.

Do you see these pokemon as traveling with the party?  Or just creatures that the PCs might bump into through the adventure?  How many charms can one character have active on them at one time?

When I first read this, I was reminded of a Kickstarter that's out for pokemon in DnD.  I haven't looked into it, and don't know anything about it really, so this isn't exactly an endorsement.  But it might be something you're interested in:

https://www.kickstarter.com/projects/rollforcombat/5e-pf2-monster-training-and-year-of-monsters

To the first part, yes. The idea is a damage type change from each once per week for each befriended pokemon. And, yeah, the BPS thing is a bit of an issue that Im going to try to fix before actually starting to invite players... Maybe by giving pokemon typings to standard monsters when the charms are used? Like a beholder would likely be psychic-dark

To the part about travelling with the party, 1 to 2 maximum at a time, and only in quests that pokemon would be related to. I do NOT want the initiative flooded with each and every pokemon theve ever met. They'll basically act as monsters, or in some cases standard NPCs that cant(usually) speak if intelligent enough. Im thinking a maximum of 3-5 of the charms? But only one can alter any specific attack at once

Ill try checking out the kickstarter, and see if it has any cool ideas or anything! Thanks!

No problem!  Your concept sounds fun, and not overly complex, which is a good thing.  I really like the idea of making the 'pokemon' types more DnD in nature, like you say with the beholder.  That sounds really cool.  There's probably a lot you can do with the different DnD creature types and their thematic spells and damage types.

Honestly, I've long held the view that D&D is good a a narrow selection of genres. With such a wide array of TTRPGs out there, (including several well thought out Pokemon TTRPGs), it seems like willful laziness not to instead learn those other systems. I've seen D&D's different editions contorted and twisted into shapes that allow it to serve specific genres before. My own personal opinion is that it's a pointless waste of time and more often than not ends up as a weaker game than the other options out there.

That said, I know of people who make the argument 'why should I have to learn a new system?' 

So, entering into that mindset I'd say that a Pokemon homebrew could work really well for a 2-player game using D&D. Thinking about balance, you could have the DM act as the world builder and the enemy pokemon/trainers, and the player as the hero in the story. That way you wouldn't need to worry so much about 'balance' and could actually allow pokemon to be captured and trained etc. Heck one DM could even then run several games and bring players from those different games into a single session for competitions and tournaments. 

That said, I don't think the idea is stupid at all. I understand the desire to create your own thing. It's truly admirable. I do think it's ill-advised, when Pokemon TTRPGs exist out there. Instead, my approach would be to explore those games and see how they can be shaped to fit your idea, rather than contorting D&D into something so fundamentally different. Or, create your system from scratch. You can easily borrow mechanics from D&D, but throw out the wide array of stuff that ain't going to work.

I really like this idea! It reminds me of Chwingas ,because they too are tiny D&D monsters whose main power lies in bestowing charms on their allies. You might want to give their statblock and some of the custom charms they can give a look if you have Candlekeep Mysteries or Boo's Astral Menagerie, the latter of which is in the Spelljammer bundle.

To be honest, though, you could give the Pokemon effects and statblocks and it wouldn't become a balancing disaster for combat if you made sure they were super weak and not particularly effective. They might need some cool defensive abilities and some might die when the player characters are fighting big monsters, but their primary role wouldn't be in those types of battles. It would be in fighting other Pokemon and circumventing encounters when hostile or indifferent creatures offer Pokemon battles.

Mark Hulmes does a great job of doing this with "Pixiemon" in Nights of Eveningstar, Season 4, episode 8, "Clyve Attains Them All." Warning: this video does include some pretty bad curse words.

Surely Pokemon homebrew couldn't be too hard. Just make a Pokemon Trainer feat that adds 1,008 unique options to find familiar and lets you swap between 6 of them whenever you bring the familiar out of the pocket dimension. You wouldn't even have to make 1,008 completely unique statblocks, you would just have to make 933 different moves and assign hit points and damage resistances/vulnerabilities based on the Pokemon. Simple.

But really, a couple modifications to find familiar is probably the best way to add Pokemon to a player's arsenal. A generic creature for each Pokemon type that you can reflavor as whatever wouldn't be too difficult.