The idea of a collectible Download Card appeals to me a little. Like if the industry set a standard for this type of thing, I'd be more willing to buy digital games.
the only way the download card would appeal to me is if the code on the card had no expiration date and was capable of being downloaded multiple times (so long as its removed from the original system)
Uh... I'm pretty sure Steam/X1/PS4 all work that way.
Steam, install as many times as you like, only one device can play (online) at a time.
Xbox One, logon to whatever machine you want to play on, download game, only system with active online profile can play (online).
PS4, Can install on 2 (active) systems. To install on a 3rd device, deactivate 1st or 2nd system.