Playing as a Fanatic Purifier. Found a great concentration of planets, didn't want to expand due to Empire Size hits. Still want to wide the galaxy clean. So plan is; conquer planets, transfer population, build them up, release as Vassal....

Only I can't release Vassal. Even if they would be my ideology, my population. Anyone have a Mod or solution to allow me to make Vassals? The button on the Sector screen says "we don't have any planets to release".