A limitation in RCT3 was that water-based transport rides couldn't go under a path bridge.
That's not true. If you placed a piece of scenery beneath the supports to a bridge, you could open it up for boats to go through. You could sometimes place a small bush under the water, or usually it was easier to place a small piece of wood above the water. As long as you had any scenery under the supports, they would disappear.
It would be nice to have an "infinite" river be curcumscribed with a park boundary with multiple stops to allow peeps to gain access to various different regions in the park.
I actually made a map in RCT3 sandbox that was entirely surrounded by water, with 6 different islands. Making perfect islands was tough because it could glitch out if you didn't leave the land around the entrance, but I made it work. I had lots of boats too, I never tried having multiple stations with boats, though. I think its possible, sorta the same as with transport rides, right? It would be a cool idea, but the guests might get confused lol. Maybe they could add a designated "transport" boat that houses 50-100 guests, with special docking stations