Ooh, I like your thinking!

From the consumer's point of view you need to make the process similar to thinks that they are familiar with.

For Brick and Mortar stores the familiar concept is a rewards card. Almost every chain store uses rewards cards. I think you could make it so that the process of signing up for a rewards card will create a new Steem account or connect to an existing one. The user can use a credit card to make purchases like normal, but the reviews and rewards points would all be on the Steem blockchain. Of course, the rewards would be in the form of STEEM and SBD, which would mean that people would become accustomed to spending STEEM and SBD for goods.

The other familiar process is signing up on a vendor's website to make an account before you make a purchase. Someday, maybe, signing up for a Steem account will be as quick and painless as registering an email address with a new online vendor. It should be pretty easy to use the blockchain for doing rewards transactions, rebates, and promotional stuff like that.

But what about the vendor's business? Where is the benefit for them? They will still need to buy POS hardware and it will still need to have reliable network connectivity, won't it? The vendor doesn't care too much about the transaction costs, they just pass that on to the customer. What they want is a low-effort POS system that is 100% reliable.