Would be fantastic to have something like a server in the docker, that will be able to download some selected games to this server (and download updates after their publish). After this other PCs, SteamDecks will be possible to download games/updates from this server.

Maybe also good to have some WebUI to control games, versions etc.

Steam already has almost all needed features for it, so easy way can be - some restricted steam version for docker, that run not in electron, but in browser.