Airports would be the first example that comes to mind. Guiding both driver and passenger to the designated pickup location, which might be separate from the normal passenger loading/unloading areas.
But throughout big cities you will have designated taxi/ride share POIs that need to be coded.
I’m sure the pricing algorithm is also quite complex.
It’s an easy mistake to make to look at something from the outside and assume the details are all pretty simple.
A coop ride-sharing app would benefit from a "wiki-map" like OpenStreetMaps which can be directly added edited by the drivers, whose pockets will see more money if maps were better, and riders who will spend less money if maps were better.
The pricing algorithm, I can see, will require a lot of advanced mathematics, and will involve a lot of politics, which might make it hard for a democratic organization to function. The politics comes from the fact that different pricing algorithm will have different losers and winners.
The success of a coop ride-sharing app seems to depend a lot on how much open-source work will programmers be willing to volunteer to the project.