2) Unreal Tournament 4, First Person Shooter. It's still under development, but they have the intention to create an official paid mod system. Someone makes a mod, he submits it to the developers to be approved, and every time someone buys that mod, both the developers and the modder earn money from it. Theoretically, this could be done with DLC outfits too.
This would be the best option, though I don't like the idea of of games being flooded with low quality things it's possible to keep it under control if its done like UT4. They could easily create different classes, you could still sell the not so great ones but don't have them visible online, then have TN select the ones they are happy with included in game patches so they're visible online. If there's any official support content quality will be far higher than casual modding as well, it's not uncommon for game developers to work on UT4 items in their spare time as a hobby.
I see a lot of people complain about cosmetic DLC, to me it seems better than the alternative. It's better for people to spend money on non-gameplay items than having gameplay compromised to try and have more mass appeal or having any sort of pay to win systems.
Even if they were to include multiplayer mini games or less competitive alternate game modes it's unlikely to be a negative, people would play multiplayer more in general.
If they had a unreal tournament 4 style shop, even if I hated every single item on there it would probably massively increase the amount of players and generate lots of money for the game. So it would still provide an indirect benefit to many people not even interested in those sort of features.