AST x GEO

My theory:

AST's require a new source of power while in the first. With no night, there are no stars from which to draw their power.

Geomancers were featured in the SB AST quests. We learn that Geomancy and Astrology are essentially the same art, but with AST drawing power from the stars and GEO from our star(hydaelyn/earth)

AST learn to channel power in the same manner as GEO. Sects are removed and instead a GEO based stance and AST stance is added. This would change spells between stances ala WAR stances. AST would still be stance locked while in combat.

This would differentiate AST from WHM and SCH while also adding in a new GEO flavor to one of the stances, essentially giving us a Pseudo 4th healer.