I'm not going to say "no", but I'll say "I don't think so". I have a much better understanding on how these animation indexes work than when I made that first post, but It boils down to memory leaks. The animation methods are all in a single line in memory and if a player magic goes beyond what its maximum value should be it starts at the beginning of the next list and continues going. You can't go "backward" through the list as these values are unsigned. Sometimes these will use the same animation methods. Enemy attacks sometimes share an animation with a particular item (happens all the time with items). Ethers might have an equivalent, but Hero Drinks might not. I can look it all up tomorrow when I get it in front of me.
EDIT:
No. There is no way to make an enemy perform the effect for Hero Drink without some EXE editing.
Too bad, but thanks anyway for looking. I think I MIGHT have found a way to still imitate a Hero-Drink-looking effect by editing the kernel: The 2 spells between Shield and Choco/Mog are unused, so I thought about using one of them to create a custom spell with 0 MP cost and give it the effect of a Hero Drink and the animation of Big Guard (this should be possible, since Big Guard comes in a later set of spells). Then I just add this new "spell" to an enemy's attack list, and since no materia is using that spell, it'll be like an enemy-exclusive ability, sort of. I hope this explanation wasn't too confusing. I'm gonna test that tomorrow.
Edit: It worked! It's possible to create a player spell in WallMarket with the properties and animation of Hero Drink and let an enemy use that.
However, now I've got a different question about enemy AI: is it possible to have a magical counter-attack script NOT trigger when hit by a specific spell? Because I wanted to let enemy A cast Wall on all enemies, but this triggers enemy B's magical counter script, making him attack enemy A after receiving Wall, which looks kinda stupid. I've looked through various enemy AIs, and I know that it's possible to have counter scripts trigger when certain specific spells are used (example: Ruby Weapon counters with Ultima when hit with Knights of the Round, but counters with tentacle strikes against all other attacks). My question: does a code for the opposite exist as well? I mean, a magical counter script that triggers against all spells EXCEPT a certain specific one (in my case Wall)? In short, enemy B shall still use his counter attack against spells from the player, but not against his buddy when he gets Wall from him.