Dang, having the customer sign for the transaction isn't much of a deviation from the current economic model. I think what the shoe store would have to do is set up a lighting network node and use lightning to receive the payment instead. That way they are on the bleeding edge, and hopefully the user experience will be impressive for the customer the first time they use it.
Thank you for taking the time out of your day to help me out, you both are definitely steering me in the right direction.
Ah yes, I fogot about the LN. I'm not entirely sure how all of that works (still need to read up on it quite a bit) but that'll definitely help you with accepting payments.
There is a limit on the LN and I don't think you can put it on a tablet as far as I know so putting it on a windows/linux machine would be necessary (it can of course be a windows/debian/ubuntu tablet instead)...