The STP I'm referring to relates to automatic roundtrips including request for quote > pricing engine > quote > order > confirmation > TMS but the real interesting part is when banks automatically back their orders with purchases from yet other banks, intra-bank. Exotic currencies add an additional dimension, as no immediate pricing for e.g. Mexican pesos in Norwegian kronors is available and the trade needs to be 'routed' through an intermediate currency, usually USD or EUR.
My view of the system didn't go beyond two banks at the time but in theory there could be a long chain. That way the banks would be forming a financial P2P network. In reality it's a pretty hierarchical network as not all banks are created equal, but it'd be interesting if you could come up with financial routing mechanisms that would find the cheapest route in a hypothetical more dense banking network and what you can learn from that for poor man's P2P networks.