The OP was not regarding any of those scenarios though, it was aimed at the pilot in the right seat doing the flying with no insurance, which would be illegal for no reason at all.
Obviously if you're in flight and you lose something which affects the airworthiness, you are technically flying an illegal aircraft, but you would not have become airborne with this defect. Of course in this instance you would log the whole flight, and you would likely be submitting a report to the CAA, the AAIB or your insurance company, so you would want the records to be correct.
This is completely different from simply choosing to invalidate your insurance because it suits your mood.