Isn't ecash the synthetic bitcoin that is used to suppress the price forever?
they just have to spin up the most credible mint and normies will go for it.
particularly since non credible mints will rug people.
Discussion
Fractional reserve will always find a way.
Be it through CEX, through ETFs, through mints...
Monero already mastered it. All other coins including Bitcoin are about to be exposed to it for the first time (not counting MT.Gox and FTX).
Protocol level privacy is the only solution.
as far as i understand it, ecash has nothing to do with bitcoin at all. you can say you back it with whatever you want as it is backed by nothing at all, you can create an endless amount of ecash.
There are some Proof of Reserve schemes that people have been kicking around for a while. That would be hard proof that the mint has the BTC (or whatever).
Also Calle has this Proof of Liabilities scheme.
https://gist.github.com/callebtc/ed5228d1d8cbaade0104db5d1cf63939
Ideas... none of them are implemented anywhere yet as far as I know.