Remove a sect? The whole draw of the AST is that it is versatile and can switch up what it is doing depending on the situation. If anything it's only real drawback far as I can see is it's MP management is worse then the other two now. So if anything I would change synastry to also give some mp back when the target takes damage just as we give some healing for every spell. But removing a sect would either just make it a poor man's WHM or SCH that has a buffing mechanic, instead of the versatile healer that can adapt to any party or situation as needed.

For spire changes, I actually have two ideas. One is that it places a buff that acts like a reverse MCH's Wyldfire. Basically it takes all the damage a target receives and gives it back to the source at maybe 25% (probably less). The other is simply to make it a decent HoT that gives AST another healing option. Which would be nice if you are in the noct sect.