M'kay, ff7rules and I have been discussing this. One can make allies appear as enemies in battle by using their battle ID as the enemy ID, but there are a lot of problems with animations and because (of course) they don't have weapons (I remember Barret turning up with no weapon, and Cloud having a sword dangling in front of him). When they do anything the game gets stuck with everyone doing their "standing" animation because it can't do the attack animation.
Does anyone know of any way to have allies as enemies other than making new battle models with their parts and giving them weapons as part of the main model?