Well we usually don't intend to elect rulers that would do such a thing. Most rulers are elected when they are doing good for the realm or seem convincing or have a large following. However, as the saying goes: Power Corrupts, and absolute power....well you know the rest.
Anyway, I could definitely see where this may have been done against me in my personal past if it were an option. If a Ruler dislikes a Duke enough they'll go to any means possible to get them out of their office or to lose their support.
I can see it happening once, yes, as a tactic to weaken a duke. But for it to become a "see saw" with the lords continually realigning their regions to the original duke and the ruler continually reappointing them dukes of their own duchies seems highly ridiculous. That ruler should be protested off the damn continent.
