you could just do this with a physical coin... It has already been done as well, look at life on bitcoin they use the physical coin to pay for gas.
There are people who are buying physical coins on this forum in form of chips.. They are collectibles, but they also work by the same way than those coins.
In fact, most of them have the private key to a wallet to 0.001 btc, or more, the price of each coin depends on how much money is loaded on that wallet.
But what is the difference as paying with a paper wallet? it is the same.