We all know the Hall of Speakers is Sigil's legislature, but who actually gets to vote there? For some reason, this was never actually specified by any Planescape products.
Personally, I think it's just the 13 factols who can actually vote on legislation. Though the factions don't have all the power in Sigil, they most likely have all the "official" power.
I'm not sure really.
I would say the factols as a must.
But how about this, only residents of Sigil who have lived there thirty or more years can vote. With so many people coming and going in Sigil, only people who truely live there get a vote.
I also believe at least one dabus should attend the meetings, because the Lady rules all within the city.