You make a good point about the existence of crypto->fiat offramp fees. I wonder if p2p no-fee exchanges would work for this purpose.
What if these small shops onboard some of their customers to Hive and offer them HBD for PHP. The incentive for customers would be a small discount for paying with HBD, for example, other than the additional benefits of having a Hive account (someone could offer free accounts for the shop), and the shop owner gets fiat to buy what it needs to supply the shop.