Honestly, just the utilization of stablecoins for interbank transfers would help with a ton. I acknowledge that it's technically possible to update the existing system to just support faster settlement, but given how long we've been waiting, I find it unlikely.

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.