IMO this argument holds a lot of merit that the player had every intention that the ball would hit him.
I've never heard of a lazy runner intending to be hit by the ball. I've never played with or against anyone who's expressed that as an aim. Get in the way a bit, distract the half-backs, maybe. It doesn't make sense - getting hit by the ball is failing as a lazy runner because you give away the penalty and risk a card - you may as well just run in from offside and tackle the scrum half.
it could easily be conceived that allowing the ball to hit him, but feign that we was somehow trying to get out of the way
He doesn't change direction or speed as he runs, from before the scrum-half picks up a bobbling ball and while. Psychically controlling the scrum-half and the receiving back line into position is not an easy conception for me.
I can see how the TMO was fooled into thinking the poor offside player was just innocently passing through
I don't think anyone believes he was there innocently. But intent is a judgement call; maybe he used amazing predictive powers and uncanny timing to position his head on the path of the ball between the 9 and the 5, in the hope that his team would... win a penalty against. In that case, I agree the blue player was put onside.
Why does this bother me? Imagine you go to a bar, a fight breaks out, you get caught up in it. The police come and the prosecution says "you went to the bar intentionally; everyone knows that there's a risk of a fight at a bar, therefore you intentionally started the fight." You'd think a judge/jury that accepted that argument were out of their minds.