It doesn't seem that difficult to pull off - take one of the existing engines, get the top y moves, choose randomly. For each level down increase y by 1.
No, it doesn't work at all. Human mistakes are not at all like computer mistakes. Like -- blundering a piece in a 1-2 move combination will straight up never show up in the stockfish move tree, no matter what you set `y` to.
It doesn't work that way. There are many positions with lots of moves that are reasonable, but many others with only 1-2 sensible moves. It would make lots of obvious blunders that an amateur human would never make.
Also attention. Lower level human players are more likely to make a move close to their own/their opponent's recent move. They're focused on one area of the board.
Basic computer opponents on the other hand can make moves all over the place. They look at the board state holistically. This can be very frustrating to play against as a human who has enough problems just thinking their way through some subset of the board, but is thrown off by the computer again and again.
It's not that bad in chess at least (compared to Go), but still something worth to keep in mind if you're trying to make an AI that is fun to play against as an amateur.
Seems this might still have the problem of moves being either extremely good or extremely bad depending on how many good moves are found, rather than playing at a consistent level. Or for example in a degenerate case where there are only two moves and one leads to mate, the computer will be picking randomly.