Would it be possible to do what some emulators do and apply IPS patches while keeping the base game in-tact? This would be great for Pokemon ROM hacks (one copy of the game, and just IPS files for each ROM hack). It could work by having some format like (HackIdentifier)_(OriginalName).ips, or maybe even just a config file per game.
E.g.)
pokecrystal.gbc
hack1_pokecrystal.ips
hack2_pokecrystal.ips
It would be useful for in-progress translation patches too, if we could just drop the IPS file in.