Since balance has no convert I think there should be a spell that helps with that so here is an idea.
Spiritual Convert 6 pips 75% accuracy
Deal 400 balance damage to target, then 500 school damage that the target is weakest to.
I think this spell really stands out other than all the other suggestions for spells because of the fact balance does not have a convert. The accuracy is that way so that it will not be spammed as often.
The spell cast shows as a convert but then out of nowhere it emits an aura of that school striking the target.