Most vending machines take IC (the NFC-style top-up cards that Japan also runs on), but ALL vending machines take cash.
It should be possible to swap out the reader, but they might be built in such a way that the entire machine has to be taken away and cannot be serviced on-site for security’s sake. I have never seen anyone servicing a vending machine in public.
This could be something that causes Japan to rethink its cash dependancy.