Nothing wrong with ecash. That's why vsome Monero devs are already working on it, as there are somevsoecific use cases where ecash makes total sense.

But: ecash is custodial. Every custodian has an economic incentive to go fractional.

And as mints all have their own anonymity sets it is likely that the theoretical privacy gain shrinks through the limited number of users per mint.

All in all. If you don't need to verify in order to trust someone it's a good solution.