So I played around with the Greyjoys for the Robert's Rebellion scenario, didn't join the war since I considered it pointless, waited it out, (the Targaryens won), and then grabbed the Independence ambition as soon as it became available. I started my war against the Dragon and crowned myself king at a point where very few of Aerys bannermen liked him (so they wouldn't join him). Only the Arryns and Tyrrels joined Aerys in the war. Then I just waited and started to eliminate Targaryen troops as soon as they landed (I fugured I deplete some of their levies and get some war score before I go on the offensive). Of course suddenly Balon died and the war ended abruptly (I guess some things still need polishing, there should probably have been an option to continue the war), but the really weird thing is that the son (Rodrik, I think) didn't inherit the Iron Islands, but the grandson (Rodrik's son) even though Rodrik was still alive. That was a bit weird.