The Emperor is reserve only in Bakka, unless you take the special character, who is 200 points and can only be played in 1500pts+. It is true that you can reserve in a dictator, and if you do so and grab a dominion battlecruiser you will have the required 8+LB for IN. They have a pretty restricted escort list, I suppose. And they can't touch all the gunships, including the overlord, surprisingly.
By the By, are we keeping the Chalice Battlecruiser? If we keep Bakka, it would fit in... swimmingly. And with which profile? A few were discussed, I will see if I can find the thread.