Well, I don't know how to use, or have--for that matter-- Brawlbox, so I can't do that very easily. >_<
But I realized that when I renamed the textures, the PAC was spelled wrong. I'm going to see if they work, and then I'll get rid of one and see if the other works...
EDIT: I tested Giga Bowser, and I think you're right; it seems like it won't work with a different texture for two different skins.
Well, what can I do for those others? Their format is like Fit___Final##.pac or something like that, if that helps define what went wrong with that.
Don't worry I used to be completely lost when I first got BrawlBox and thought I'd never be able to use it, but now I know a lot about it. If you need any help with it just ask me.
I don't think it will change it; you need .pac files along with their .pcs counterparts for all transforming characters.
I don't know about the others I just know Giga Bowser can't have textures.