Yeah, that's an interesting case. My initial reaction is that I'd think of it as a tool that the AI was using. If a human used such a tool I'd consider it cheat

Yeah, that's an interesting case. My initial reaction is that I'd think of it as a tool that the AI was using. If a human used such a tool I'd consider it cheating at the game. But a self-modifying strong AI could integrate the specialized go AI into itself. If that is not considered cheating, should it be considered cheating for a human player to integrate tools into their physiology? Today it's pacemakers, why not a specialized go chip with a neural interface tomorrow? And this is assuming the strong AI even has a concept of a self separate from the software it controls; that separation might not even make sense. I think we might not be able to answer these questions until a strong AI emerges.