Trams in parks (i.e., Trolleys, Double-Decker Buses, Horse Carriages etc.,) would be fantastic.
But having said that, I have a suggestion for trams as well as monorails and/or trains... I would like the option to make them mandatory or optional.
What I mean is... Currently, if you wanted to build a "parking lot" with a spawn location or two, separated from the theme park itself perhaps via water (think Disney's Ticket & Transportation Center as an example). Now let's say you had a monorail and (maybe Frontier will put out a new ferry in the futre?) to take peeps to the "entrance" I still have to connect the "parking lot" to the entrance gates via a pathway. If there is a monorail and/or ferry, but no pathway exists between the parking lot and the entrance gates, the peeps will just leave and never board the monorail (or ferry.)
I would love the option to "force" the peeps to use these transportation systems. In this case, you could toggle the parking lot tram "optional" but the monorail (or new ferry) would be "mandatory" as there's no other way to get to the "main entrance". When guests leave the park, same thing in reverse.