Didn't the GBA version also fix most of the bugs that FFVI had?
They fixed the Evade glitch (Blind is finally a status effect) and I think they banned Gogo from the Merit Award this time (no more Wind Gods), but you can still make Cyan go batshit insane, rock General Leo for the floating continent without the need for external devices like Game Shark, and Relm's Sketches will still break the game in the literal way.
Additionally now you can give everyone Ragnaroks and Illuminas through legit means rather than item duplication (which you can still do), learn Mog's Water Rondo dance in the WoR, and have an esper provide a Speed +2 bonus rather than needing to keep Odin (still doesn't make grinding speed worth it though).
Really the only meaningful changes were the Translation (good), the usual ROM Hack bonus dungeons (because Squeenix heard that you weren't grinding enough), and the tinny and poorly compressed audio quality and washed out color pallet (bad).