Replacing Weapon Animation With a Spell

In my hack, Gau eventually learns the "Fight" command. 

When he learns Fight, I want to give him an equipable weapon, like General Leo Edition did with the Wild Heart. However, I'd like the weapon animation to be that of Pummel or Moogle Rush, both of which have been cut from my hack.   Does anyone have any ideas of how I would intercept an attack animation for a single item and replace it instead with a spell animation?

This might be difficult with the vanilla Fight command. Weapon animations are a little more limited than spells and other attacks, so I don't think it would be as simple as changing the animation properties of a weapon. You could try modifying the Shock command at C1/BB49 and C2/171A. There is also a pointer at C2/B4CC that you would need to modify. You could also try writing a new weapon animation script, maybe a combination of the unarmed script at D0/7EF9 and the pummel script at D0/6EE0. Or maybe there's an easier way to do it that I'm not thinking of...

Might be moot. If Gau still has Rage as a command, it'll overwrite his weapon animation each time he uses it each battle, changing it to whatever weapon the monster attack is set to look like.

...Which is honestly cool because you can set enemy attacks to a bunch of random weapons and Gau will pull them out of hammer space, but it will pose a problem if you're setting up your pummel animation by weapon ID.

Everything's approach is probably best; give Gau a new command that is titled 'Fight' but works like Shock, triggering a custom spell/move with an animation of your choice. There might be trouble with damage scaling, though, if you call a spell that isn't the 'battle' spell. You'll also have to include said new command as an exception in the Magitek and Fanatics Tower command overrides, starting at C2/532C [though the special case skips you want to add to start at C2/535E].

...Though...
You're probably low on available commands, so perhaps a subroutine special case for Gau in the existing fight command is called for. It'd be similar to Umaro's, except instead of a variable branch you'd run one subroutine for Gau that functions similarly to Storm, but with damage calculated from his weapons like Charge.