Well, you mentioned that having the recruitment fair anywhere else than the capital would be very costly in upkeep, so the incentive to move the capital to the front would remain the same.
Eh, details. That sort of thing can easily be adjusted to achieve the desired effect, once the basic mechanic is in place.
As to the rest...I dunno, I'd like to see colony TOs return, but I think they might need some reworking to make a bit more sense. And if you're suggesting that we shouldn't allow secessions when the realm is below a certain nobles:regions ratio...well, I might well be persuadable that that should be a thing.
