Don’t see why it has to be an NFT or why proving customer ownership (other than confirming and recording orders/purchases) is important then. It’s practically no different to buying soundtracks, wallpapers or other game related merchandise/media no? 
I suppose in an actual NFT, you would own these cards and be able to resell them to other traders, but the way you are leaving that detail out in your posts like the last one:
…makes me think that is not part of your idea.