I having one of those things... Ya' know a picture with words...
Heroic Games Launcher could be the answer. The GameVault devs wouldn't need to reinvent the wheel with a Linux client dealing with all the proton sand boxing. Just add to the heroic launcher.
Looks like someone has already had a similar thought too...
https://github.com/Heroic-Games-Launcher/HeroicGamesLauncher/issues/2951
ROCK AND STONE!