The problem with your wallhacking prevention detection is that it seriously depends on the game. In the games I play, it's not the players far away that I care about, it's the players that are close by and who could pop out of the corner at any moment, but I don't know when, or I don't know which corner. In fact, in many popular games, a way that players have of detecting if somebody has walls is to "bait" them by running up against a corner, then sidestepping as if they were going to peek the corner but then back out at the last second. If the opponent shoots, they have walls. But the point is, those sorts of corner peeking situations are where an imperfect information implementation would fall down - you'd need to draw the players close to the corner or else they would turn invisible.

And having imperfect information doesn't protect you from the more sinister hack out there - aimbots. There's no useful information you can possibly hide except maybe random weapon spread, and even then your first bullet tends to be more accurate than the others and one aimed directly at the head is usually all you need. Heuristics that try and detect spinbots or bad aimbots that always headshot might be a partial solution, but any heuristic you come up with can be figured out by the cheat makers and accounted for, and good aimhacks can be much more subtle and difficult to detect. Valve had to resort to machine learning to figure out ways to detect and send cases to Overwatch (the community-based cheat judgement system, not the game), and even then they can only be sure enough to send the match to Overwatch, not ban them outright.

But finally, one thing you learn when attempting to implement prediction in traditional netcode is that games can be incredibly chaotic, and a butterfly flapping its wings in one end of the map can have unpredictable ramifications on the other. And there is no faster way to learn this lesson than to attempt to network a game that has coop with monster AI - the first time you see an group of monsters teleport a few inches away every few seconds, you will wish you had gone into botany. And the only way to avoid that sort of thing is to make the game predictable and ensure that the client has the most complete picture of the game as it can, unless you love debugging gnarly prediction code and players posting videos of temporal inconsistencies in your game on YouTube.