By season 2 it would have bombed so hard that they would have to resort to writing in an overused story line like another Borg cube/Romulan renegade with a WMD to try and sex it up.
That's true of any show - it's just lazy writing. I do think this sort of thing would need to be a limited run though - and be well planned out in advance.
I'd be aiming for a 10 episode season and have the broad outlines of a 3 season run in place.
10 episodes a season is enough to both have interesting stand alone stories and to put threads in place for a big end of season storyline climax. The events off S1 would be felt in S2 but would also mingle with a new storyline and then the driving storyline of S1 and S2 would intersect for a big resolution in S3.
Keep it small, smart, well written and well plotted. Have a definitive goal in sight. Tell the story you want to tell and then leave it be.
If it's successful you could pick up the threads in a follow on series and take it in a different direction