A Crazy spell idea from a sleep addled mind

So I had a moment of either lunacy or genius. how about a spell that gives various bonuses depending on subjob? It would be Enhancing skill based potency of course, but say for 500 skill, this spell would give a +attack % if /drk (say 10-20%), mab if /blm (+10-20mab), mdb /whm, conserve mp /sch. /war probably wouldn't give a bonus, or share the same as /drk due to Temper. /nin would give maybe +dual wield, thf +eva (it would need to be a truckload to be worth it though) /pld for def. (gogo rdm cocoon+1?) im not sure about the rest, but the idea is that rdm itself is a jack of all trades, your subjob is a focus. so rdm/blm can still do a bit of everything but its nukes are stronger then rdm/sch. rdm/drk(war) hits a lot harder, but rdm/nin hits a lot faster. the best part about this idea as far as i can tell is each job bonus could be rather large since there is 0 ability to stack them, you cant get the atk bonus /blm or the mab bonus /nin and so forth.

(Edit)
So i took a bit of time to hash out what it might look like both as a spell and a ja

Specialty (JA)
Duration 3:00
Recast 5:00

Forte (spell)
70mp
Duration 2:30
Recast :30

The hard part is effect potency...would the ja or spell be stronger...i think the spell would because of the enhancing requirement, but who knows.