Would a Federation warship like the Defiant out gun a Star Wars Star Destroyer? Who has a bigger armada? Who has the tactical advantage? Don’t forget that The Federation includes the Klingons, who love warfare and have fast, agile, heavily armed ships, with cloaking devices, and the Vulcans with superior logic and tactical planning.
The UFP would agree to a treaty with the empire and the latest ship called “Enterprise” would spend a lot of time near the border trying to secretly help the rebels without being caught being directly involved.