Hi there. I love your Hack idea but I have 4 issues.
Issue 1:
There is no scope to show Pokemon Mechanics. Eg: Most of the Pokemon you will have will have moves like Punch, Kick etc. Their abilities will be Huge Power or Intimidate. This is because there aren't many Pokemon moves and Abilities which fit the theme of Marvel
Issue 2:
There are no evolutions. Like maybe Thanos can become Infinity Thanos or HOTU Thanos and Iron Man can evolve into different suits but what about characters like Deadpool, Luke Cage, Iron Fist, Galactus, The Whole Guardians Crew etc. There are gonna be almost 120 Pokemon with no Evolutions in a Marvel Pokedex of 151.
Issue 3:
There are literally no type combinations. All the Hero Characters are gonna be Normal/Fighting types and all the Villains have Dark, severely messing with the type balance of the dex.
All of these issues can be seen in a ROM Hack called Dragon Ball Z Team Training. Its a similar idea to yours, its Fire Red but with DBZ Characters. It too suffers from the issues I mentioned above. Its a great concept and the creator has put in alot of effort, but these glaring flaws ruin the experience for me.
Issue 4:
You seem to be an avid Spiderman comic reader (considering all your ideas from above all have characters closely related to Spiderman, rather than the whole Marvel Universe eg Uncle Ben, Kingpin, Captain Stacy). It may be better for you to make a Spiderman Dex than a Marvel Dex because you know more about that section of Marvel. And don't think that's a small section because the SpiderVerse alone has 800 different characters to make Pokemon of.