I agree that Ibladesh could definitely support quite a few more nobles. The gold is there, easily. As for adding more regions, I think Ibladesh is pretty close to the max it could easily support. It already has the nobles to support more land, but has several rogue regions it never bothered to take, despite a desperate need for more food.
As for the Ibladesh military... Well, Ibladesh has put their entire army against Caligus ever since the start of the war, and Caligus still owns Isadril and Hamadan. If Ibladesh's army was as good as you're claiming, then this war would have bee over a long time ago. The fact that it's not, is very telling. Ibladesh's military is OK, nothing special. No better or worse than just about any other.