Very interesting.
Maybe it would suffice to add virtual operation for such events and collect statistics to present on list of witnesses, similar to missed blocks?
Could a witness that is bending the rules just not issue any virtual ops that would reveal they are bending the rules? So it would still look like they have connectivity issues or something?
It doesn't matter. Vops are just a way to formalize what is already visible in the logs. So yes, witness bending the rules might not generate vops exposing such activity in the account history / HAF node he operates, but every other node will still see the problem and show it. Just like missed blocks are assigned to the faulty witness by every other node, not by the witness himself.
Oh, great. So sounds like vops can bring the non-consensus activity to the consensus so that all nodes can check what all other nodes are doing.