Community Controlled Used Game Marketplace
One of the biggest differences between going digital and staying with physical copies of disc is the price of digital games. This is largely due to the fact that every game you buy is essentially "new". A used market should be set up and the community should control the prices, albeit microsoft can intervene shall the prices to get too high or too low but that way the digital marketplace can compete with the likes of GameStop and BestBuy and other places who sell used games. By allowing the user to set the price point of games that they put up on the marketplace, it allows a little freedom, maybe i want to sell it to a friend but I don't want to sell it for the average used price, I can drop the price a little or maybe I can set up a trade and say this game will sell for $29.99 or another game can be traded for it.
Salmon Mode commented
Or...you know.... they could just have better sales, and something like a rewards program for buying stuff in the first place, rather than screwing over developers, publishers, consumers, and MS for no real reason.
There's no such thing as "used digital games", because digital games don't get used. They don't have any problems with them over time or through usage like a physical disc does. They only lose value when people don't want them as much.
If I sell you my used copy of Crackdown 3 in disc form, you are accepting that it's had my greasy fingers all over it, been scratched quite a bit from being put in and out of the disc tray, game case, and/or other surfaces, maybe had stuff spilled on it, and you also accept that the box will be damaged to a degree, the cover will be worn a bit, any codes in the case will be redeemed already, the city map will be gone or damaged, and so on. You are getting something worse less than what you would buy at the store because it is not in as good condition as a new copy.
With a digital copy, literally none of that applies. The digital copy literally can't be damaged, or lose any more value than a new copy would have. So there are no "used" copies for digital games, and if something were to be labeled as such(literally a lie) there would be zero reason to reduce that price because it's every bit as valuable as one not labeled as such.
So instead of taking money from publishers, and developers, and getting an extremely small portion at that, and also SERIOUSLY complicating things, a rewards program could be used to suit this entirely. If we got points for every purchase we made, it would be essentially like this, but way easier, more straightforward, and more beneficial to everyone involved. In addition to this, better digital sales could be used to encourage more purchasing from people. This is also easier, and benefits more people.