If you had the power to add one feature no questions asked, what would it be?

[Guillermo]

But... Spell 1, 2, and 3 IS the classic, original style, I thought?

Ah that's possible, I haven't played the first couple FFs but I just remember from all the FFs I have played that fire-fira-firaga... etc. always was a thing.
In any case, I'd argue that just having spell 1, 2, and 3 is not as interesting as having the name of the spell evolve with it.