Yeah, this is my issue. If I am allowed to take down the Dark Brotherhood, why can't I take down (or take over) the Thieves Guild and sock it to Maven? God, I REALLY hate her, haha. I hate her even more since I cant get rid of her smug self.
It seems that there is no quest line to take down the Black-Briars in Riften. Its either support them or ignore them. (Please correct me if I am wrong!) I'd like to see a mod that add in a quest line to take down the Black-Briars and "clean up" Riften. Or take control of it your greedy self, which ever. :)