None of that is a given with central custodians, which very often already have to comply with regulations concerning money laundering, embargo enforcement etc.

> (instead of the awful SWIFT)

SWIFT is a real-time messaging network.

International transactions being slow has almost nothing to do with legacy technologies – it's partially outdated processes (batch processing facilitates netting, and netting preserves liquidity!), but overwhelmingly that we (or at least the regulators making the rules) want them to be slow enough to be able to intervene in case of financial crimes.