Keeping food warm in the air
Well I presume they will be wrapped in the same foil that burritos you buy the old fashioned way are, so I don't see why keeping them warm should be a problem. The problem will be that it is a lot less efficient to take a minute per delivery (and that's being optimistic) when you can serve many times that number of walk up customers.
This is a ridiculous gimmick of no practical value whatsoever. Yeah it'd be fun - I'm sure I'd order one that way once just for the hell of it. But next time I'd go to the food truck and get one much more quickly.