Hi,
I think if only one thing were to be changed it would be to remove Aegis of the Hearth. It is arguably the worst spell in the entire game. I think spells should be a paragraph, or two at most. Aegis is a half-page of special rules and cases.
Instead, I suggest a rework of parma. Much as parma can be extended to protect others, perhaps it can be extended to protect a place. This would reduce complexity since we already know how magic resistance works vs parma.
Rich