1. The conciliation premium is apparently split across all currencies. Is this split evenly according to some normalized exchange rate? Or could it make sense for the split to depend on the payer's endorsements?
2. For that matter, the system apparently needs to know that X amount of ETH is "worth" $36. Where does this information come from?
You might imagine we start by assuming that there is a global market for each currency. In that case, yes we can just accept the market rate. After all, if the market rate for currency i were below the vendor’s rate then the customer might be tempted to arbitrage by buying more currency i. But quickly this becomes untenable as all currencies become bundled. In that case, a new mechanism will have to be found to determine local market value. One tempting way for a shopkeeper to determine this is to follow their supplier’s endorsements proportional to the amount they buy from each supplier, and to follow their customers proportional to the business of their customers.
Or could it make sense for the split to depend on the payer's endorsements?
change the total value they feel like they’ve paid / the vendor feels like they received
change the composition of their the outgoing payment