I'd be ok with maybe a system like merits (though i'd prefer not to grind for them but w/e) where you can enhance a skill a certain amount of times, or have a certain amount of total upgrades.

whm: Better/cheaper cure? or longer/more powerful regen/stoneskin/protect? or better enfeeb DoT on aero/stone?

drg: increase crit rate? or longer life/power surge? or extending life surge to part?

etc, i'm sure theyd have much better ideas than i would, I'm personally just looking forward to more jobs to provide that choice