Expanding the chatter system to include more npcs, and the chatter itself to be drawn from a pool specific to that npc (ie a Sinner would know about stuff related to/around Sinn Street and those NPCs) or occasionally just be a random bit of lore.
This could be even more interesting since these rumors don't have to be true, and you'd get people parroting stuff in public and then being shamed or possibly getting in trouble for making stuff up. Perhaps how likely they are to tell you a true rumor or a false one could be based on the already pre-existing 'qualifiers' for chatter, but expanded upon.
And to make this more feasible, it could easily be crowdsourced; players could easily write rumors of all kinds about NPCs, areas, factions, history, whatever, submit them somewhere privately, and all the admins would have to do is read them over and approve the ones that fit. This could be a great worldbuilding tool and plot-instigator, and would also help with that common problem of 'I've worked here a year but I still don't know what that receptionist is called even though I see her every day."