The ultimate "anti-cheat" is playing on some trusted party's computer. That can be a cloud machine, but I think today a game console would work just as well, turn that closed nature into an actual user-facing benefit. Console manufacturers seem focused on their traditional niche of controller couch gaming and not on appealing to high-FPS keyboard-and-mouse gamers, though.
XIM fakes being a controller but is KBM. I sort of wonder whether it’s possible to use a camera to get a stream of the game and make an aimbot either by making a fake controller or a robot that manipulates a real controller.
True that wallhacks aren’t possible via peripherals, though. You might be able to get some level of info from the audio output and map knowledge, but nowhere near the same as true ESP.
It doesn't even seem very hard to implement, steam already has the ability to stream games, they could add this pretty easily as an option for any game (although there is the concern of the extra cost of running the servers).
That shouldn't be a problem if all players, regardless of the OS, are required to use the same cloud service with similar latency.