I think there's an answer to this, which is to separate the inventory service from the game servers. Keep the same inventory service online, reuse it for all of

I think there's an answer to this, which is to separate the inventory service from the game servers. Keep the same inventory service online, reuse it for all of your games. Any official servers and any vanilla servers will validate that you own the cosmetics you use, modded servers can override this but you can't use your cosmetics everywhere unless they're actually registered to you. (Or possibly the clients validate it too in which case even a modded server couldn't override it for every player.) And (as with several other things being discussed in the comments) of course Valve has already done this, and offers it as a service: https://partner.steamgames.com/doc/features/inventory https://partner.steamgames.com/doc/features/inventory