I am amazed reading this thread that no one has mentioned obligation yet. You have a built in game mechanic for when the Empire is going to come calling. Give them 30 or 40 group obligation and just bide your time until that unlucky dice roll...
I try and keep the response bound more to the canon reaction of the world, and less the rules. I already know the Empire's going to retaliate at some point I was just asking when they would canonically. Duty/Obligation is useful but I don't let it make someone act out of character so I wanted to double check that it was in character for the Empire to bring down the hammer when they're so preoccupied.
Edited by Rozial