I am always a little perplexed by the view that pilots would be better off by flying Command on light pistons first. If I was asked which was safer, flying an Islander (or even worse C-206) single pilot in PNG, or an Otter (two crew, turbine powered etc) I would go with the Otter.
I would say the Otter would be safer as well. And yet, as far as I know, NCA have had only one fatal crash with their fleet of bugsmashers. Look at the last half dozen aircraft on that list of PNG prangs. A fair representation of two-pilot, two-engine turbines there. Arguably, two engines are not always better than one, and likewise, two pilots may not always be better than one. (I think two pilots and two engines are better, most of the time, but there are issues with two-crew ops that don't exist with single pilot ops).
But I digress. The point is, the person in the right hand seat may have thousands of hours of experience, but not a single hour of command experience since they did their CPL training. And FO experience is nothing like command experience. I think FO time beyond about 500 hours is worth very little, while all command time (especially in PNG) is invaluable. Some may disagree with me. Fine.
I can't prove my opinion, but I stand by it.