Ok. We were playing a scenario and it ended up that the Imperial player only had an e-web while the Rebels had all their heroes. Based on normal play can the Imperial player hold his activation or does he have to activate on his first go around and let the Rebel player get three activations without being able to do anything?

You cannot normally save an activation no.

Ok. We were playing a scenario and it ended up that the Imperial player only had an e-web while the Rebels had all their heroes. Based on normal play can the Imperial player hold his activation or does he have to activate on his first go around and let the Rebel player get three activations without being able to do anything?

He must activate the E-Web at the next opportunity and the Rebel player will get multiple activations back to back. You cannot hold back.

This makes sense, since otherwise they would need to have rules about the double pass situation (would it end the round? etc.).

Also, this is why many people consider the number of Deployment cars you have in your list important in Skirmish, since you can effectively "Do nothing" (very little) and setup multiple unstoppable activations.

The order would go

Rebel

Imperial

Rebel

Rebel

Rebel

If he was to pass then that is it until the next round