The problem with this is you want to turn every dwarf into Belegar. Now one might ask, how is that a problem, Belegar is great? He is indeed, but he is also a deeply troubled dwarf because he won the hold of his ancestors in ways his ancestors would probably not approve of. If you need halfliings and wizards to reconquer Karaks, what is the point of retaking them to begin with? Not to live in them certainly, there are plenty of other holds with room in them, the entire dwarf population would fit in KaK.
Of course we the players who have read the Thorgrim interlude know the answer to that question, to get more power in the network, but that is not going to become common knowledge anytome soon.