I think what can u do is creating a protocol that let 2 system communicate, for example, a protocol that have both system spec, in case u want to transfer amount from address in sys A to B, protocol need to evaluate how address amount in A is equal to address in B, (A amount is USD, and B amount is EUR), if A have 100 USD want to transfer to sys B in EUR so B need to create new address for address in A amount equal to 93.60 EUR, that address should be store and linked to Address in A in the protocol.