I think that people are very much Idealizing Sylvania.
It is miscast central, it has been stated multiple times in quest that the air is so choke full of Dhar that it sets even the most experienced spell casters on edge.
I don't believe it would be conductive to any magic research except Dhar.
The locals don't and won't like us, it would a lot of AP to gather good will, and they would rather we won't mess with their business. And I'm not talking about the vampires, I'm talking Codrin Petrescu, about a man who led a campaign to get a bunch of people killed. And the population that it had taken us a 86 final result to get them to tell us that it means "piss off".
To quote the man -
"There are two kinds of people in Sylvania," he says softly, as you walk side by side through the valley. "Those that would willingly serve the vampires and necromancers, and those that want to be left alone by any would-be masters."
It is going to be a very diplomatic intensive position, we are not just going to juggle a bunch of Knight egos, we are going to need to convince Sylvaians to work with us, and the surrounding nobles to work with us.
Also, out of the current top options it is the least mobile one, It is the one least conductive to if we want to meddle in anything outside of Sylvania. We have a very narrow scope.
And, if anything, it is more likely to entrench us in stirland, if only due to the combo of narrow scope, and the AP sink and time sink involved.
With the empire building involved there will always be just something more to do, and there is no way the thread will trust another human enough to leave the position.