Creative help with changing basic elemental/cure spells?

Hey there. Good day? I hope so.

Spells like Fire/Fire2 and Cure/Cure2 have very simplistic use in-game that isn't very involving. For example, having the stronger Cure 2 renders the original one somewhat obsolete is most situations. Same goes even more-so for the elemental spells. There's pretty much no reason to use Fire1 over Fire 3 ever again later on.

It'd be nice to change these spells into each having unique strengths that depend on level, while at the same time never allowing any one level of spell to go obsolete. For example, I'm thinking of potential for there to be a unique situation in which it is appropriate to use Bolt3, but there also being another situation in which Bolt1 might be even better somehow. However, I'm having trouble thinking of anything that can be implemented effectively in-game. Other than the cheaper MP cost. So I'd like to ask you guys for any ideas..?