I've spoken to Eastland drivers -- I've been riding with them for years -- and thats exactly what they do, minus the complexity. They announce an address over radio and the closest driver takes it. I don't remember how they enforce this policy in the company (sorry), but they do and it works.

As a customer, I don't have to muck about in some app, especially while buzzed, to get a car. I call and get a real person and am done in 5 seconds. No app can do that.

Admittedly, it works because they have a lot of drivers. I can see how this becomes a problem when you have many smaller companies and you need to hail the closest. Thanks for the perspective.