As a user, I'd love to be able to deposit and withdraw stablecoins at banks - this would enable essentially instantaneous transfers, and provide an interface that anyone (including non-banks) could interface with.
> It feels like slow movement of money in our financial system causes a lot of these problems
I'd turn that around and say that the hyper fast trading causes a lot of these problems, and in particular creates more problems than it solves.
Introducing a Tobin Tax and replacing continuous trading with frequent auctions (maybe with stochastic end times, to limit sniping) would alleviate a lot of these problems, and put the rent-seeking HFT traders out of a job, while not impeding the important price discovery and capital allocation functions of the market much at all, I think.
https://en.wikipedia.org/wiki/Tobin_tax
EDIT to add: Appropriately enough, Wikipedia says:
> Another term for these broader tax schemes is Robin Hood tax, due to tax revenues from the (presumably richer) speculator funding general revenue (of whom the primary beneficiaries are less wealthy)