See I've been thinking up a caster DPS build for Geomancer, and basically came up with the same thing as you, but in reverse.
Casting earth element spells while the Earth Seal (ground based AoE) is active, increases your Earth gauge while reducing Wind/Water. Then you spend the Earth gauge when you cast Quake. Same for Flood/Tornado for their respective elements. One is mainly AoE, the other two are meant for ST.

So I'm all for it in theory. However I think a healer having three different DPS spells used in rotation is going to be the big hurdle here, given what the're doing with healers at the moment...