I think hard mode isn't a solution if we consider that there will be extra grinding involved.Do you want a challenge in FF? A better solution is to ditch level up systems and stats or cap the level the characters can achieve but it will end up like a puzzle game after a while.

Being harder and requiring a semblance of real strategy from the beginning and throughout the game in general would make most FF's better.
A real strategy is just a theory, , there is always going to be an obvious solution. There isn't any game in the market where i make a compelling choice in every battle, we are talking about games which have 100+ encounter.

Bottom line :making it harder won't make it any more fun.