Those who purchase digital games are free to resell them, the Court of Justice of the European Union has ruled.
Finally some good news! I've been waiting for quite a while for such a ruling.
Edit: Seems this cites an article from 2012, I didn't notice that (and it's still news to me). Though there's still hope that it'll happen, EU is slow, but usually eventually gets shit done.
They literally just need to add a way to "repackage" a game from your library into an inventory item and then they could use the Marketplace they already have
It would be cool but they probably wouldn't pay money directly to your bank on sale. It would still be locked to Steam. Wish valve let you transfer money out.