Hmn, that sprite hack of FF5 advance...
Shouldn't that technically work for the PC version too, since it's basically just running the GBA version in a fancy wrapper?
VI too could be done this way. Somebody get this guy over to the FF Modding Community on Steam, a modder was working on replacing 6's sprites (I think they're ok, but everyone is disgusted so I must be the weird one), but they got ill somehow.
They've got documentation of what they're doing, it just still needs to be done.