So more of a blockchain KMS then? I don't see how you could construct such a thing.

The requirements of allowing a publisher control of their game for some time (for example, allowing them to retract some keys when violating the EULA, but not all keys when "unpublishing" a game), but also allowing people to resell keys, which are somehow publically accesible but only for the legit owner, and the owner has to allow third-party acces without publically sharing a private key.

This is the age-old identity problem with blockchain. It's all well and good that Bob's name is written on a smart contract, but that doesn't remove the issue with how to identify Bob.