So, how/when do you get the W10 code though? They might send it upon XB1 code redemption. If so, you can't sell the XB1 copy and keep the W10 copy, because it would likely go to the person redeeming the XB1 copy--that's just my guess. However, you could probably team up and try to share a purchase with a friend or another CAG, like with the Smash DLC for Wii U and 3DS.
I don't like that thought, though. It makes gaming the system too easy, and I'd worry that abuse would scare future developers/publishers away from this. I'd rather see it as automatically tied to the account of redemption. That said, I could potentially be on-board for this. Get it digitally, use the Home Console sharing to let my brother-in-law play it, then give the W10 code to my little brother.