Adapt the keypair generator to a 3d printer that prints the private key QR inside and forgets it immediately as the card is printed. The public QR can be printed on the top (4th) layer along with an anti-counterfeiting device of some sort. The inner QR code can only be accessed once. Here is a basic thingiverse QR:

https://www.thingiverse.com/thing:46884

This would solve both the durability and privacy problems.

Putting this mechanism inside of a vending machine could open the possibility of selling BitCheques in the 3rd world - and elsewhere. It may even be patentable.

Anyone interested?