If a single character repeatedly leaving the lordship of one region for another over a short span of time is undesirable, then perhaps some kind of mechanic should be placed to support this. I can think of a number of potential options:
* A noble that voluntary abandons a lordship (even if it is to accept an election or appointments), loses some prestige.
* A noble that voluntary abandons a lordship (even if it is to accept an election or appointments), is unable to become lord of their old region for XX days (a long time).
* A noble that voluntary abandons a lordship (even if it is to accept an election or appointments), gains flaky points and a noble with lots of flaky points is more likely to have a region they control rebel against them.
* A noble that voluntary abandons a lordship (even if it is to accept an election or appointments), gains flaky points. Flaky points reduce the amount of food/gold produced by any region under that nobles control.
* When a noble voluntary abandons a lordship (even if it is to accept an election or appointments), their old region becomes less productive for a while.
Putting something like one of the above in place would surely deter nobles from region hopping and if region hopping really is such a bad thing, then it is probably worth the effort to disincentivize such behavior!
