The third would retain a standard that's unworkable, but it would shift the burden onto the accused. The best thing to do is to get rid of the standard, but if you want to keep the standard, it needs to be clear that the burden is on the accused to show why he couldn't possibly have foreseen the likelihood of harm. Making the Crown prove that beyond a reasonable doubt is impossible. It's a very high threshold to prove that beyond a reasonable doubt.
That's what we do in the context of the mental disorder defence. An accused who's saying they are not responsible for a crime because they were mentally ill has to prove it on a balance of probabilities. I would say the same should apply here. The courts have upheld that as constitutional in a case called Chaulk and Morrissette.