Create new phone contacts for taxi/public transportation/uber-like companies with different rates/vehicles.
For example you could call a taxi from anywhere on the map at any hour of the day and get different rates based on the time of day/distance from player/distance to travel/player preference (pay more for speed/convenience or wait some time for lower cost transportation)
The player could rent limos to host parties/events to boost marketing for existing businesses. Buy tickets to fly to new cities. Buy passports to unlock new importing methods/companies. Lots of possibilities here.
I would add a “real” bus system. Right now it seems the subway is too limited. The catch is it should stick to a certain route. want to know what bus stop(s) you need, use the map, turn on the bus routes and it’ll show you.
If I want to get to a certain place, check the map for a route, go to the nearest bus stop on that route. If you have to go across town, it would require multiple transfers.
Also have to option to buy a monthly bus pass.
I thought of this while I was running from the hospital to the nearest subway (lol).
Atleast, that was how it was like before they put the subway in in LA when I lived there.