I absolutely love your "Fortification" idea.
Its unique and that is something that AST currently needs.
Merging the ewer with the spire would be awesome, and it would leave an open door for another buff.
I would change your spire idea though, instead of adding a regen effect, in my opinion it would:
Increase target's spell based hp recovery by 10% (so you would be able to help your fellow healer just like SCH helps with fey illumination)
I wish SE could take a look at these ideas :/