I think a movie like that would flop, because it would be the same ole / same ole. It would also interrupt the canon facts of the original two shows.
Now a series called 'Federation Space' could be interesting if it focused on a different Federation planet, colony or outpost every week. The series could start out in the 'Enterprise' timeline and progress thru each of the series timelines using the canon facts as a guide. That way you could see 'observer' POV of each of the series.
The Q could be the tying factor. It could kick off with a movie that 'visits' each ship in its time with the Q in undetected observer mode or something...