I just thought I'd point out something that I'd misunderstood about the Rapid Mobilization mission.
It's not just used to move the Rebel Base.
It's also used to move up to 5 units from one system TO the Rebel Base without having to be adjacent to it. I'd assumed that you got to move the 5 units to the 'new' Rebel Base when you move it (so that it wouldn't be empty).
Suddenly this card is going to be getting a lot more use in my games. :-)