essentially this is what i am saying. those who need certain training to be grouped together so they are focused on more, hopefully receiving greater benefits

Same guy can do this though if they are half decent. You don't need to focus on big guys and little guys like you do with skills.

I think we are also over stating the effects here by getting into the detail, interesting as that is.
It isn't the case that just because the props may be concentrating on bulking up and overall power, that they will simply burn out after 20 minutes. Fitness doesn't just focus on one area.

There are of course cases where someone like a Gledhill will need to get bigger simply to compete with people in his position, but that can be done without losing all his stamina to go the full game. It is as much about how you play the game as it is how fit you are. (I think someone has already said that). The wrestle techniques being used are as much about saving your own energy as using the attackers up. When you grip right but gradually lower them to the ground you are resting (especially with 3 doing it) and the rest of the team are also resting, whereas just throwing them to the floor allows the one runner to sap the energy of all the players then having to chase him down.
I'm certain that if Korki were playing in the back row (not that you would want him to) he could last the full game. He isn't piling into 3 defenders and trying to wrestle with them when playing out wide. So it isn't that he is unfit, we just want him to concentrate on a particular area.

So back to the point made above......if we want the team to better in fitness terms....we need someone who understands the game as much as they understand the science of the human body. In this area, we shouldn't be looking at someone from another sport to try and get a new angle. We need good basics and get a proven fittness/strength expert with experience of rugby league.
I'd actually do what Huddersfield did and find someone doing a good job and simply offer him money to do the same job with us. Even if it means playing with one less player in the squad because of the cash needed.