Extra transport for our city area would be cool. I'd make a prop tram line with tram stations using plugins, but I'm not good at json - besides, real trams running would be so cool. You can have them (if you chose) in the rich areas. The tram track could be above tje ground too, like the roads.
..... or new train station designs so not all of the train stations look the same. Maybe a city centre train station with room for two train tracks so passengers can go separate ways.