IMO the only solution at this point is for resellers (especially for higher value red stamps) to use the flashlight method to redeem the code and then send the ERC-721 to the buyer's ETH address when they mail the stamp.
This is going to hinder ebay sales, where many buyers and sellers aren't crypto savvy, but hopefully shouldn't be much of an issue for sales on this forum.
I haven't decided what I'll be doing if I resell my physical stamps but I am considering this.
In one way, it's actually a feature because you can keep the physical stamp in 'mint' condition and still redeem the ERC-721.