International FX exchange made easy, and automated

 Btc, an infinite block chain, does automatic FX exchange priced according to congestion. We just need to make a finite block chain.

We can use the fundamental property of Sam Walton theory of the checkout counters, and make this work just like the automated, profitless S/L trading pit. We have buyers and sellers who trade spots on the finite block chain and an automated pit boss which is neutral.  The interest swaps, in this case are partial spots held outside the block chain.

Senders of currency are borrowers of ledger spots, receivers are depositors of ledger spots. The pit boss only maintains its own holdings of partial ledger spots, keeping them bound in total. This works just fine and I will provide details over a few more addendums to this post.

This is just like the automated S/L because instantaneous swaps of partial ledger spots are just like instantaneous interest swaps needed to keep deposits and loans in approximate balance.