I don't think being able to swap Sects during combat is where AST is really shortcoming, tbh. I see this brought up a lot as some kind of magical cure-all bandaid for the problems it has, and I can only REALLY see it being a benefit to a Noct AST (by virtue of being able to place a Regen on the tank to sustain them for more DPS uptime, a la how SCH's fairy currently works). It would have virtually no value for a Diurnal ast, who would likely be running with a SCH anyway to provide the mitigation. At best, it could be used in a DF scenario with a WHM/DiAST combo, but if it can be done in DF odds are you don't need mitigation anyway.

I wouldn't care if they added the functionality at some point, but I don't think the problem with AST is that they can't Sect-dance. It's that SE lazily copied WHM and SCH with it to begin with.