(Apologies for the video that probably wouldn't fly in 2006. The desync is awful. Areas of silence are "attempts" to resync.) Well look at that, I'm not just trolling in the Under.
GBA map animations are boring. Blue guy bumps into red guy, red guy does the same back, and one of them might do another bump. But after taking a peek at Nightmare, I think I figured out the alternate pointer in the spell association editor. Edit that and you can play a map animation. Staves and some consumables have this pointer filled in, and if you give another item that pointer, it will play that animation. I took notes of those offsets Nightmare shows, and I'll share them here.
I should warn that only heal and sleep have been tested, and fortify makes the enemy just vanish afterwards (he was OHKOed, but it might cause glitches), and it has a lot of issues right now. It plays on all attacks on player phase, including the enemy's attack. I haven't tested what happens when two weapons with animations fight. They also don't work on enemy phase, but that might just be it going off the enemy's no map animation. It is based on weapon, so weapon-based classes probably won't find much use of it, but maybe FE4-style map animations for magic might be doable in theory.
(Also steel swords are seriously messed up on my rom and only plays the magic sword animation, so you get to see Ereshkigal cast from it.)