Can't imagine Sun's idea being any harder to put in than Double Shot for RNG Was. I do however think the MP cost of the second spell should be halved, especially if it will be a "Random" Stance.

I don't think the idea of random stance, Especially if say.. You're Buffing Stoneskin, Phalanx, Protect... So a stance with random proc would kinda suck and blow your MP a lot if you had to rebuff with it on.

Alternatively, Double Cast could only effect nukes and Cures, Which then would only really hurt cures, If you're trying to Cure IV someone and it double casts, over-Cures, and you're out the MP.

I think a simple Job Ability, on 1-2 Minute timer, casts a spell twice back to back (Despot style)... Would be the best bet. or, Double MP Cost + Double Damage. (Sch gets an Ability similar to this though).