There's just no way that this wouldn't force a shift on the entire industry to the detriment of consumers.
Games that aren't already "games as a service" will cease to get developed just about entirely.
The vast majority of players (90%+ I'd imagine) who buy singleplayer games would also sell them quickly. The vast majority of consumers (95%+ I'd imagine) are going to buy the cheaper version of the game, even if it's just 10%, 5% or even 1% cheaper. If the resell system's visibility and usability is good, anyway. You get the exact same product, after all. The fewest of customers are actually invested enough in really wanting to support the specific devs and all.
After a year, when millions or many thousands have played your singleplayer game and most of them already resold the game or are still trying to, no one's gonna care for the devs offerings. However low they'll go, some resellers will get below because making 1$ back is better than 0$ and they are 'done' with the game. So yeh, no long legs, tails and what have you. By then the devs have likely sold a negligible amount for several months. Well, i actually think I'm generous with that time frame. I think within a few weeks it's already going to be reduced to nothing.
There's no comparison to physical reselling of games, still. I mean, you can compare it, but to actually argue that reselling your digital game with a few clicks within literally seconds takes anywhere close to the effort of handling the selling and shipping of physical games would be ridiculous. No, the latter is not some "huge" issue. But digital reselling would still be a thousand or million times easier and more comfortable. And easily fully automated!
In reality, forcing the option of digital resales is not consumer-friendly the second you think any further than the direct "oh sweet, I can sell this thing I got back now!" If this were to become reality, then there'd no longer BE this thing to sell back because no one would bother to create it anymore.
That doesn't just apply to gaming, of course, but all software development. Which is why I can't see this getting through in the EU.