With that, it would be interesting to have a very close knit of duchies who call the, "states" of a federation or something yet they are all different realms. It would be like having 5 senators (rulers) who would speak for their state (realm) and try to coordinate this and that. Perhaps very effective military wise as 5 realms would have 5 recruiting centers..
Anyways, back on topic! Just threaten them and beat them up a bit until they agree to more satisfying terms
Thats what Madina already is... but just not with 5 capitals, just one.
Governors(dukes) have full sovereignty over there duchy, the being part of Madina is all about swearing to the Constitution which is everything.
The Rebels defied the Constitution and now made them selves an absolute monarchy.
Twainville could be a nice place for them to sod off to.
lots of food production that will all be sold to the Republic as 'absolute' monopoly.
yeay, long live capitalism!