The only tools I actually use at the moment are the hex editor HxD, and the python builds for compiling things, and the new PGE for Emerald.
Personally I would swap to Emerald anyway, there's no limited functionality over Fire Red to be honest. I would say the only thing thats in Fire Red and not Emerald is the dynamic OW hack, which admittedly is awesome, but will be ported by us eventually.
Currently the problem with sprite changing is that it has to be tied to your current pokemon, and the transform code is very confusing. The problem with Illusion is that it only has the sprite and name as changed, but keeps the base stats of the original pokemon which is a bit more tricky,
yeah probably ill be back hacking for a month or so hopefully i can do something. I saw the mega evo thingy if that works maybe we can do it for illusion but using ditto transform for reverting back and stuff although i dont have the slightest idea on how to do it I dont even remember how to script rofl
Hey! Unfortunately not, I haven't reaaally been hacking in awhile. It's still one of the more difficult things to implement because its a graphics change. If theres a chance its with the EM Battle Engine!