I use Ifrit as a SMN when I feel lazy, because he can just sit on Sic and be as just about as effective as he can.

The only things I feel should have a toggle for SMN though is Garuda's Contagion, because she really loves to use it the moment any of your DoTs goes on the target, and possibly Ifrit's shield, because it going off against enemies that don't trigger it, or when they're doing long casts is a complete waste...
Ifrit's stun not so much as most bosses are stun immune anyways...