For instance, it's possible that a currency based on long chains of debt is prone to massive blow-ups. That's modern day fiat currency. In contrast, cryptocurrencies like Bitcoin are not based on debt.
> Come up with a currency anyone can create and there you have a real disruption.
If I've understood you correctly, something like that does exist. See Ethereum and its ERC-20 tokens.
Here's an interesting one, an attempt at decentralized UBI where each individual gets issued individual "coloured coins" and participants accept currency based on a web of trust: https://handbook.joincircles.net/about/whitepaper.html
I think this direction is very worth exploring. Today fiat currency is generated through creation of debt between banks. Most cryptocurrency is generated through validation of transactions (be it PoW or PoS). The idea of moving currency minting down to individuals in a way that can maintain a sustainable inflation is very attractive to me. The really hard part is squaring the triangle of no privileged centralized parties with censorship capabilities while neither being vulnerable to sybil attacks or locking out disenfranchised minorities from the economy.
Circles is the only serious attempt at that I've seen and I'd love to see more innovation and critical analysis in this venue.
Trust on the currency comes from real life trust. A bank for the Euro. A human for a novel human-made currency.
Then, Exchanges that trust 2 different currencies can buy/sell those currencies.