What's wrong with making them well rounded multi tasking death bombs?

You don't NEED to specialise in any particular area, and it only takes a short amount of time to level up your weapons/magic when fighting strong monsters...

I give everyone a copy of all the useful magics - Cure, Life, Esuna, Basuna, Holy.
I let everyone be as powerful as each other without restricting anyone's abilities...

The only thing I don't like is there only being 1 Ultima spell - so I'll have to decide who to give it to. *flips a coin*