This is fertile ground for someone stepping in and creating some PoS specialized hardware that emulates a card and process ecash when it's given to it.
Discussion
With KVAC (which I am currently working on) you'd only have to flash 1 single nut (coin) into a card or emulated card. Since it's fixed size, it would almost never fail to write, and would take a constant time for a receiver to process it.
nostr:npub16lcw8ytugeh3ug3na93yl0tdf0gnjtduljhn2a852atf6jtvkucs7pruje I think this is the way