Every shader depends on both the driver version and the model of your GPU itself. Which means a lot of shaders. I think Valve had a version of it though but not without issues (GBs of shaders to be downloaded)
The Steamdeck does this thats why it doesn't suffer from stutters.
For normal PC's, realistically Valve/Steam are the only people who could solve or implement this for PC games as they have the tech and platform to distribute it all. Even with all that its a crazy task to try and solve due to all of the variations and new patches for games that require the shaders to be recompiled again.
The idea here wasn’t to share the compiled shader, but to share the shader configurations that each game uses — the ones that are used to then compile the actual shader. So you would compile them all at game start from the configurations you downloaded
To my knowledge, the massive size isn't from the drivers, but because transcoded video files are also slipped in with the shaders. Proton struggles with things like Media Foundation, so Valve transcodes videos on their end.
For normal PC's, realistically Valve/Steam are the only people who could solve or implement this for PC games as they have the tech and platform to distribute it all. Even with all that its a crazy task to try and solve due to all of the variations and new patches for games that require the shaders to be recompiled again.