A simple secure element for bank clearing

I deal with the problem of a small collection of banks clearing branded crypto coins at par over a distributed point to point network.

Each of the N bank has a simple secure element that contains the public keys of all corresponding banks servicing the crypto coin as custodial units of exchange. Banks have a simple protocol:

Take these coins
OK, here are your coins in return.

With all the appropriate timeouts.

Each bank maintains a queue for clearing any of the other N-1 banks.  Clearing requests occur when the custodial coin is checked in or out, or when clients deposit custodial coins from another bank.

When a particular queue for clearing lengthens, even as all the queues are service round robin, then a ledger fee is raised for clients depositing that particular brand. Queue length must be stable, though differing brands have differing liquidity series; resulting in a difference in queue size.

The secure element, for a small number of banks, say 100 max, is a manageable process, current hardware secure processors can implement the protocol.