This “will save against fear” thing doesn’t sound right. The gorgon might be frightening indeed, but no regent has ever had to roll a will save to decide opposing him. Likewise, a commoner might not have to roll against fear to contest his tyrant’s rulership unless he’s been particularly traumatized, with torture or family kidnappings, or unless imminent conditions give him reason to be fearful (and not just concerned or doubtful - I’m talking pathological fear). A suitably-armed rebel group will have no more fear of the king’s army than they would have of the vos, who torture and murder their victims habitually, though they would certainly try to be prudent about things. They just wouldn’t find themselves mentally paralyzed the moment they thought of defying the king.
Otherwise, I can’t find any fault in your feat, exept perhaps the taxation leeway bonus. As I see it, people will still want to rebel to escape their hardship, and they’ll do so the first chance they get - perhaps the presence of soldiers in great numbers should be required for the loyality bonus to take effect. That is, taxes can only be increased one tier without a penality when the province hosts at least one unit per three province levels.
Anyway, I love it. Here’s another one:
Isloationist: You prefer to keep yourself out of foreign intrigues, and would prefer that others treated you the same. As such, you control no more than one holding above level 0 in foreign provinces per province you own, and foreign regents with a foothold in your domain control a total level of holdings no higher than the number of provinces you own. You also have no more than one international trade route per every six province levels you own, and per every internal trade route placed firmly within your borders. You rarely engage in diplomacy (no more than one treaty created or accepted every turn for the last five turns), and have treaties with no more than five other realms. Careful not to let your domain slip into outsiders’ hands, you gain +5 to all attempts to contest foreign holdings in your own provinces, and a +5 to the DC of having your own holdings contested here. Since your people are “protected” from all outside influence, it becomes that much harder for regents to agitate (+5 to DCs unless they’re native to your realm) and you receive a +2 to your own agitate actions, when performed strictly within your own domain.
This feat becomes disabled during rounds in which the regent creates or accepts treaties, or declares war on another realm. This feat is also disabled when the regent ends his isolationism by falling short of the pre-requisite conditions.
Powerful? I honestly think it’s a bit under-powered, what with all the demands and restrictions. Plus, it’s only suitable for military governments. It sure is nice for role-playing the goblins and the orogs, though.