I have always wondered why the automat didn't come back in style, especially in these days where people will be happy to just swipe a card in a reader, grab lunch from a drawer, and go their merry way.
The biggest issue I see (mainly because its easy to pay with credit cards) is ensuring that food is on the shelf for its recommended life, then promptly pitched.
I just think there is a market for automats, expecially in heavily trafficed areas of a city. Staff needed would be minimal, a janitor for the dining area and restrooms, a couple chefs for the kitchen, and 1-2 people to maintain the infrastructure. Because staff and people are separated, the chance of robberies is low, and with a camera or two, vandals would be promptly caught.