Nick,

Understood; though I'd call fraud coercion, the use of the word is a side-issue here. However, an AI improving humans could have an equally clear view of what not to mess with: their current goal system. Indeed, I think if we saw specialized AIs that improved other AIs, we'd see something like this anyway. The improved AI would not agree to be altered unless doing so furthered its goals; i.e. the improving was unlikely to alter its goal system.