Well, they wanted to keep Aeonar's magic because they wanted to use the Veil tears to determine guilt or innocence, or something. It's in the codex.
Not what I meant, I meant that building something the scale of the magic-blocking vault door on a building scale should be something both templars and mages would totally want, given the alternatives. Yet, they haven't. They're missing some key knowledge here that would actually let them build something on that scale.
Actually, it can. Otherwise, there'd be no such thing as a loser who reinvented themselves, and those do happen--they happen far more often with mentorship. Willpower isn't some fixed, set thing that never changes after you're born.
No, you're right. Willpower can rise and fall. But it's not something that itself can be trained as one would train muscles. If it was, things like depression would not be a thing so many are struggling with, even with therapy.
Then we train them to be better at resisting demonic possession.
To quote Optimus Prime: "Were it that easy..."
Seriously, you think the First Enchanters liked sentencing people to tranquillity? You think they liked signing the forms of those willingly requesting to be made tranquil? The mages in the Circles did everything they could, but some people just don't have the strength of will required to fend of demon all their lives..
So they would let the good mages in question continue living outside the Circle?
Provided the mages have viable method of continuing to do so that doesn't screw over anyone who isn't them? Yes.