How do you plan to tackle this mentality, where there is such hostility to anything in the slightest bit unusual?
Less cheekily, I think Kong like instruments when properly adapted could capture the best parts of local currencies (like the Bristol Pound), the messy parts of multi-governmental currencies (like the Scottish Pound), and the nice bits of computer validation.
In your example specifically, the Royal Bank of Scotland can still mint Scottish Pounds but back them on chain by UK pounds.
I'm of course hand-waiving the problems here - we've made a programmable monetary instrument. One can program things well or badly to support this kind of interoperability.
Also, while I do sometimes have problems with them abroad too, it's 50/50 - I've had them accepted in all sorts of places, including India, Nepal and China
Literally every bank in the UK will accept Scottish bank notes - if that's not a defacto legal tender, I don't know what is.
https://en.wikipedia.org/wiki/Banknotes_of_the_pound_sterlin...
But in the real world, they are absolutely defacto legal tender - as above, every bank in the UK (and even many beyond) accepts them.
However, the old Swedish notes had not lost their value because they could still be redeemed.
In a formal legal tender situation, you could to some extent require a private party (within the relevant jurisdiction) to accept the notes in payment of a pre-existing debt. You could contrast this with "having value", "being redeemable", "being in circulation", and "being widely accepted", maybe.