It would be nice to add a new type of quest when we belong to Gondor, then we can be ordered to go to Rohan and help fight their enemies. And the same with other alliances.
Also, I would like to add that if Gundabad has an alliance with the Erebor Dwarves then you do not get tasks to kill your own allies. I and some of my colleagues have just such a problem. It's not that annoying but it would be nice to change this detail.