It sounds to me like you’re describing a healthy natural phenomenon called “evolution” in the biological world and “forking” in the open source software world. If a large enough segment of participants want to start playing by a different set of rules, when each participant holds their own chain, they have the option of adopting a new ruleset and taking their history with them into that context.

But the point is, if you cheat the original rules, there’s a signed record of it, and others playing by those rules will reject any further transactions with you because their copy of the rules automatically enforces them. If you have a whole section of the network choosing to play by a new set of rules, they can do so, but they can no longer reliably transact with anybody playing by the original rules. So in essence the currency has forked into two currencies.

To me, this is a desirable trait of natural evolution.

And I’m not quite sure what you’re saying about gateways to non-digital fiat currencies… A mutual credit currency is a closed loop — all accounts adding up to zero. I could do a crypto credits transaction with you buying dollars, but that is the same as if I was buying toothpaste or server hosting. The cryptocurrency transaction happens within the currency transaction chain accounting, the outside currency is the product changing hands, in this case. It doesn’t affect the rules of the transaction chains. Can you clarify the concern you have?