You are right that it is "one" more thing to track - hence why I believe an app that handles this automatically is needed in order for this "model" to really gain some footing...
One of the key points with this idea - is that I am not converting their FIAT dollars into bitcoin and then offering them something back in return - they have to pay in bitcoin to be eligible for the deal in the first place - if they could do it through an app with smart contracts integrated into it - this should "in theory" all be able to be handled through the app.
I am really glad you brought this up though....as I sit here typing this I remembered another extremely important point about accepting bitcoin and utilizing it in this way...
The business owner does not need to "make" any additional FIAT value on the collected bitcoin in order for this model to be beneficial - I am going to work on another post later today about this and get into a little more detail as it is extremely important...
More to come....