The GBA is superior to the SNES, so of course it could handle it if they bothered port it If you want to see a demonstration of power of the GBA, try playing Tales of the World: Narikiri Dungeon 2 (japanese) - that has the same beat-em-up type action battle system as a PSX game in the same series (Tales of Eternia) and is just as responsive to controls, and still looks good

I find FFTA a bit slow to my liking in battles, but that doesn't stop the battles being good I'm sure I'll finish it long before it comes out in England, if it ever does, many of the better non-FF RPGs on various platforms never made it here