I have done it once - managed to bribe an army in Denmark, kept the province, and managed to take out Norway from there. Think I was Welsh on that campaign, but it knocked out the Vikings, and I could get on with the serious business of trashing the English factions without hordes of Nordics messing up my plans!

I have a method of farming rebellions which involves moving one army between two provinces - always have a defensive battle for each rebellion, and you end up with a specialist defender general at the end of it all, when the provinces finally settle down. Keep one very small broken unit as your garrison in the province next to rebel, and that keeps the rebel army small. Don't be afraid to screw up the tax if you're going to have a rebellion anyway!