It's not too much, I just used the same strategy that was used for the "FC 05" patch. FC 05 manages its own variable that keeps track of who was the last party member to damage an enemy, but that variable is not cleared upon success, which is what that patch fixes. FC 01, 02 and 03 respond to commands (e.g. Fight), spells (e.g. Flare) or items (e.g. Dried Meat), respectively. They each keep track of two battle variables; one contains the ID of the caster and the other contains the ID of what the caster did. I thought of clearing the "caster" variable, but then I figured that clearing the "what they did" variable would be more reliable. I know that FC 04 does something similar, but it responds to elements being used, so I figure it doesn't have a problem because I believe most physical attacks are branded as non-elemental.
Other than that, I'm not sure. You should check out Assassin's bank C2 disassembly if you want to see for yourself.
We have EVEN MORE themes now, but some old ones are gone...