Comment by recursivecaveat

This is already done in Valorant at least (and presumably other games I'm not as familiar with). Unfortunately you are strongly limited by network latency. Imagine you're standing up against a wall next to a door. You expect if you step 1 foot sideways to instantly see the entire room and everyone within it. Hence your client already has to know everyone's locations in the room or you will get pop-in. You can limit people's ability to get truly implausible free information, but pretty much any-time someone is rounding a corner there is an unavoidable period of game-breaking free information you have to give the client.

If you look at the bottom gif in this post you can see what a huge advantage a wall-hack still is: https://technology.riotgames.com/news/demolishing-wallhacks-...