Not sure how comfortable people are answering this, but are there quests / will it be possible to help Imperials rather than fight against them?
It may sound silly but serving the Empire has become important for me so at the moment Imperials being the antagonist is a deal breaker. I'll be damned before I let a bunch of rebels take over Rom..I mean...The Empire...yeah.

If it makes you feel better, the background information given on the Daggerfall Covenenant claims that they're fighting to restore the Empire. Otherwise, the Imperials are just a 4th, non-playable faction, and there's no reason not to believe that at least some of the PvE quest givers in Cyrodil will be Imperials.

There is no Empire at the time, it ended over a century earlier with the death of the last Akaviri Potentate. Without a central government there can be no rebels - who would they be standing up against? The throne is empty. It's a time of ruin, war, bandits and countless pretenders to the throne.

It's understandable that you want to side with Imperials, but think about it: the man who found the Empire you know and are loyal to, Tiber Septim, was not an Imperial himself - he came from the north. Nobody cared, he was powerful and he conquered Tamriel. Whoever is stronger rules the Empire and it's not always been people from Cyrodiil.

But yeah, there'll probably be some Imperial quest-givers in Cyrodiil.