I actually don't want to see Caligus destroyed.
I would prefer it to still exist and perhaps another realm made out of Fontan city. Caligus can still exist out of Domus.
I feel the same way about Sirion, they do need to be dealt with and taken down, but not utterly destroyed. You can make a couple of new realms out of their horde of land in the North
I feel game play and dynamics will be better with more realms, rather than only a few massive ones. Im not talking about puppet realms either, but ones with their own agenda and standards. It will also make politics more interesting.