Great idea centralizing the drop of stops and doing that every 200m or so in a grid, especially at places of interest. Now you could make the self driving cars a little bigger so they carry more people. You could even connect several cars. At that point you can basically add a safety driver back in, with 20 ride sharers its still 95% self driving (compare that to Waymos that have uncertified safety drivers remoting from the Phillipines for 20% of the time). Run them on a predictable, frequent schedule, so you dont need an app to call them.

Finally make them drive in a separate lane, on iron tracks and make them draw their energy from an overhead wire for maximum efficiency.