That would be excellent. Discounts could be offered for "riding out of category" or "mixed passengers." That way people who don't mind mixing with Inquisition Identified Witches (IIWs), plague deaths, and oligarchs for the public guillotine can save some cash, while those preferring to ride with their own confederates and have the cash to spend can pamper themselves on their way from the Bastille/pub/protestant cellar/tower/dungeon/bath house.