pulse
You are bang on! As I have said a number of times, the best appreciation of the weather over sea - approximately where the ac was at WP change - was that assessed by the yachtsman (1-2 miles off shore). The ac was visible (ie below cloud) at about 3-400 ft (probably more) and the visibility was hazy about 1nm - very much VMC (by JSP/AIP definition ie COCISOS) but probably close to mil UKMLFS limits for Low-Level flight. Therefore, the crew were probably not negligent before the waypoint change.
The fact the ac crashed into the Mull in cloud is indesputable. The fact that the ac probably climbed into cloud is also almost certain. What no-one knows, is what happened between the WP change and the crash, nor why the ac climbed and, certainly, whatever did happen cannot be proven with the requiste burden of 'with no doubt whatsoever'.
What worries me about the RO's logic is that the BOI report 'cannot discount the possibility' of technical failure, control restriction, distraction, visual illusions yet then discounts these statements in their series of 'possible rates of climb scenarios'. Ultimately, they say there are a number of possibilities and uncertainties but then go on to postulate a 'probable' cause.
Flawed logic perhaps - cherry picking maybe?
Either way, the ROs had no basis on which to find 'gross negligence' with the required burden of proof.