I would also do with the strategic capital move rule, because that too can be gamed, and I've seen it. However, I would implement a new dynamic to the distance from capital penalties. Allow people to move their capital to a border region if they want, but have the game calculate the most central point in the realm and the realm's radius from that point, and then add extra penalties to all regions that are beyond that radius from the capital. As such, if a realm was 7 regions wide with the old capital in the center and decided to move their capital to the border, inflict considerably harsher distance from capital penalties to all regions more than 3 regions away from the new capital. Therefore, you could do away with that rule that is too easily gamed, and have a fairer game that will passively balance those who would move their capital on the border to help them in their war. Such new penalties should be exponential, though, to make sure that the regions just outside of the normal control radius aren't too severely affected while those at twice the distance of the control radius and punished in a crippling way, because it's not always possible to have a capital in the most central region of the realm (as it may not even be a city).
That's an interesting idea. I'm not sure how well it would work, though. It would totally screw with any realm that did not have a nice, geometrically centered city to be their capital.
