Or... perhaps you'll just be presented with a bunch of lockers, and only the locker with your order in it will open.

This sounds like a problem that can be solved immediately, and when 20% + ~$5 is currently going to delivery fees for these orders, it's going to be easy to get people to go to some extra trouble.

For its first year of existence, Uber Eats in my city didn't require drivers to go to the door of the user, so it's something that already happened millions of times without anyone trying to force it.