At this time, this isn't really possible. However, I've passed this along to our POS team, and we're hoping to add more features to the POS, and this would certainly be a welcome addition to the platform. Thanks for the suggestion!
Yes this is a huge oversight. As if you swipe a card that isn't associated with their account it creates duplicate entries in the system. And they have to put in their email for a receipt. The customer is very annoyed to put their email again.