Can't you do all of that directly in lightning. lnbits+ntag424 chips? The nation currency backing would still have to be implemented somehow (e.g. open a future contract on lnmarkets?), and that middleware could do the necessary api calls for the card/chip/wallet.

Putting that aside for a moment ...

The problem I face here is mostly that onboarding merchant is difficult/expensive.

They need to provide tradfi terminals (so they still pay banks their cut) + now they need a specialized device for lightning (if they don't run something with android+good nfc reader; which is rare here) + the chips.

Unless merchant is bitcoiner, my experience is mostly good only if I say it won't cost you anything to provide this payment method.

When they see how it works, we can get into things like gift cards, spend only mints etc. But that almost never happens.