I could get behind these traits being implemented. There are a ton of ways they could make it balanced. Materia, potions, stats on accessories (just make sure they're not job-locked). If they ever get some kind of class-neutral talent system going (which would also be cool), it'd fit well there.

I could also see them making this part of a new tank or healer's minor mitigation toolkit. Various killer traits as a tank levels up, that activate about as often, and about as effectively, as block or parry, and throw in an ability that buffs the % for 20 seconds. Or a spell a healer can toss on a player/whole party that averages out to be Eye for an Eye/Sacred Soil-ish.