I would love if Valve developed a multiplayer server system for CS2 (and maybe generalisable beyond that) that only sent other players' locations when they were very close to being visible to the player, and sent audio and damage events in a way that only gave soft information away as well.

So if you snipe through a wall, instead of sending the location of the shot source and direction, the server has to do slightly more work - calculate who got hit and what noise everyone should hear, but then the client doesn't need to know the location of the firing player.

I know it's not the only way to cheat, but the fact that the client has all the information has to be a large factor.

This is a really old idea. It was implemented in CS:GO in ~2015 [0], although community anti-cheats like SMAC have implemented it for years before then [1]. Riot have an article about their implementation of the same idea in VALORANT's that a good read from a technical perspective [2].

Sadly, CS2, from what I've gathered, broke this.

[0]: https://www.reddit.com/r/GlobalOffensive/comments/35zwwy/opt...

[1]: https://www.youtube.com/watch?v=qkhQgYB4lAA

[2]: https://technology.riotgames.com/news/demolishing-wallhacks-...