Getting rid of Maven would sink Riften's economy, considering the Black-Briar meadery. Besides, Riften's already under Stormcloak control, so unless Ulfric's going to get rid of Law-Giver, which would be a stupid decision considering she's one of his supporters and he'd be unlikely to hold Riften if not for her, there's no way to get rid of the current Jarl.
After the war I think you should be able to persuade/intimidate Law-Giver to cut off her connections with Black-Briar. If you fail you fight her and replace her with a new Jarl. After that you drive Black-Briars out. I can't see Riften economy getting hurt if you give the meadery to man who is in charge on it anyway.
My character isn't "good" so my reason for liberating riften is just to see Maven's head on a plate. I hate that [censored].
For me, if a quest of this caliber were to exist, it should be in conjunction with the TG questline (may be asking a bit too much of this game but w/e), where you're likeliness of "converting" Riften so to speak, would be influenced by your stature in the TG. Say, for example, you finish the the questline and become master of the guild, then you should be much more likely to keep the economy afloat when you drive out the Black-Briars.
IMO, the TG has more power and influence that black-briars as they are the BB's tools most of the time anyway. So if we rebel, then what do the black-briars have? Oh I happen to be in the DB, and the Thalmor ain't got anything on me. I'll kill those damn elves in the blink of an eye.
So I guess I still fail to see what's stopping me
