I think it would be interesting to require the management of wastes.
For one, it'd be another need you'd have to fill for your Dorfs - something more to do, I guess.
It could be handled via just a dumping labor - collecting/replacing and emptying chamberpots, like - or you could get fancy and build GREAT DWARVEN SEWERWORKS. Possibly which could dump into a magmapit or something. Alternatively your Dorf-toilets could flush with magma. Fear the bidet.
If an area isn't properly sewerified/chamberpot-worker-attended, you could end up with dorfs throwing it out into the streets, like how it went in medieval cities (I think? My history is kinda bad), thus giving you a dirty slum where diseases would breed and fester. Dwarfy solution of periodically flooding the slum-tunnels out would be cool, too.
Alternatively, you could dig cesspits, and have to change out every so often due to filling up I guess. Sorta like with garbage dumps, finding real estate that's close enough to be convenient but not close enough to be smelled might be an interesting challenge. Uh. I guess. Alternatively you can of course drown your enemies in it like most are wont to. Afterwards you could flood the countryside with it. Fertilize your flowers, I guess.
I'd want it as an init option, though, definitely. I'd also rather have bigger stuff in first, like improved hauling/minecarts/dumbwaiter-lifts-and-trams.