I think it will be hard to visually indicate where the different PPs are, in relation to the rider, in a way that makes it easy to find and join them. The PPs can be in a different route in Watopia than you, so such indication is only helpful if the rider is on the same route as the PP.
What I would have liked, is to directly join any of the PPs without having to leave Watopia (exit). Then I can just start a ride in Watopia, select my bike, do an easy warmup and then join a PP. My current activity would have to be automatically saved and a new one started with the PP.
A natural place to access this “join PP” functionality, would be on the pop-up menu and with keyboard shortcuts. Press the button, select a PP (same popup as from the select route page) and you are automatically taken to the PP of your choice.