[Other] Is this possible/simple?

[Dapplegonger]

I'm not sure if I will actually be committed to this in any way, but is it possible/in any way simple to mod a ROM of a game to make it so the Pokémon types are all correlated to the Trading Card Game's type system (i.e. Onix is fighting type, Gastly is Psychic type) along with weaknesses and resistances? I want to leave everything else unchanged.

 

[int]

Yes, check out Gen3-Romhacking Suite by karatekid in the Tools, Tutorials & Resources section.

 

[Dark Shadow 6]

Yes you can do that with Gen3-Romhacking suite and with hex editor, i prefer hex edit but it is very hard to learn and use.