I think those NFC enabled "tap to pay" will be the next big leap for pinball, assuming manufacturers can be bothered to give them wifi capability and they're vended in wifi enabled locations (which is pretty much everywhere these days). Put the NFC receiver on the lockdown bar with a small logo so people can just tap their phones to it to enable Apple or Android Pay. Might as well add a credit/debit card swiper too. That can go on the coin door though.
No coin drop, no bill validators, and instant money transactions. The Op wouldn't have to run around town collecting money from a cash box. I imagine a lot of people wanting to play a game or two, don't, because they don't have any change in their pocket. That's been me more than a couple of times.