Hmm.. I Don't Know i Can Envision Conjurer's having a "Secret order" of Geomancer's who are "Nature's Avenger's"... Nature is Kind and nurturing, unyielding and strong. You Piss it off and it will END YOU.

I'd See the first ability they get as a "Stance" that give's them a Stacking Mechanic like Defiance does, that they can trade-in for extra Damage abilities (And Possibly borrow from Monk's Abit, Make it do increased damage on spells as it Stacks) This "Elemental Fury" would also as someone else Stated Convert some Spells into Damaging Versions instead. (Esuna into an Inflict/Bio Spell, Medica into an AoE Poision/Aero, Cure 2 and 3 into Attacks.)

Also rather then Ground Based Target Spells... Have them as Target Based DoT-AoE's. Tornado would Have a Bind Effect on it and do AoE too All in range of it's Primary Target, Quake would Slow/Paralyse all target's in it's Range Etc. Point is The Idea is Workable... Just not in the way Stated by the OP.