If there is a Necromancer who can build creatures like in this game, some changes there would be good:

Additional modifiers on parts. Right now all parts are the same. Hunting for parts would be more interesting if they had modifiers like +%Health or +Offense, +Damage, +Defense, even having additional skills, maybe. That would make a dilemma when swapping out parts. If it had been in the game, it would also have made Jonaleth's quests more interesting, you could have had fixed unique bonuses instead of a part you could find in a random crate.