The biggest problem is detecting cheating. How do we as other players KNOW someone logged into another account? How do we KNOW people collaborated on moves?
The only way to know when players have logged into another account would be to log when each account has logged in and see if the login location is different to where the player normally logs in from. This wouldn't be definite evidence, but it's better than nothing. As for knowing then people collaborated on moved, it's impossible to tell assuming that people that collaborated on the moves didn't inform anyone that they had collaborated on moves.
Shouldn't really add rules that can't be enforced. Counting on someone's word alone isn't great.
I'm not an official, just a late responder.