This is actually what lichess does - if it flags you as a cheater, you are silently paired against other cheaters. They have almost the entirety of the lichess

This is actually what lichess does - if it flags you as a cheater, you are silently paired against other cheaters. They have almost the entirety of the lichess system source code publicly available, but from what I can gather they have a private set of weights on inputs - I assume to prevent cheaters from fully reverse-engineering the system.