I suppose if you have a Tyranny government, so you can hold all the government positions yourself. And are able to deal with the lack of estate support somehow. And can defend the realm against monsters yourself. And can endure the mind-numbing boredom of being a one-man realm.
Strongholds are indeed a good alternative for colonies, provided you have the right stronghold. Storm's Keep and Valkyrja are good. Balance's Retreat... is not.
