Specifically for fire emblem fates, but I’m not picky.
Are fat mods for 3ds even possible?
Unfortunately the closest thing I can think of is the better bosses and amiibo mod that gives more lines of dialogue during lvl up death retreat etc. to best girl Candace. Also I know I’ve seen mods that change models, I’m specifically thinking of one that adds DMC5 Vergil as a recruitable unit so I’m sure it’s possible. If you plan on making one good luck. If I can make a suggestion, again if you’re thinking of making one yourself, try making a romhack for one of the GBA games cuz that’d be much easier.