http://en.wikipedia.org/wiki/Antiking
I know in this example it purely refers to the HRE, but I'm wondering could it be an interesting mechanic for succession wars. Instead of these wars being a mish mash of alliances which equal tier dukes fighting a unified king, the leader of the rebellion could be declared an anti-king, given king-tier status, and thus having all his supporting dukes as vassals. This would increase his income as well as given him primary control over their armies and their levies. There could also be the option of enticing the rightful king's vassals away from them.
I know in this example it purely refers to the HRE, but I'm wondering could it be an interesting mechanic for succession wars. Instead of these wars being a mish mash of alliances which equal tier dukes fighting a unified king, the leader of the rebellion could be declared an anti-king, given king-tier status, and thus having all his supporting dukes as vassals. This would increase his income as well as given him primary control over their armies and their levies. There could also be the option of enticing the rightful king's vassals away from them.