Very good assessment.I see what you are saying, normally a lot of teams used to have a FF, CHF and a resting ruckman when using 3 talls, Crows are a bit of an exception.
I agree that that most set ups like this will be too slow to be able to lock the ball in forward 50.
I think Curnow is the key to making it work, he is so good at ground level the often crumbs his own contests that is how well he moves, Mckay also is a lot quicker than expected.
The beauty is that Luko can play wing and a variety of roles, we may even be able to roll Charlie through the middle, Mckay can pinch hit in the ruck so there is a lot of flexibility if things are not going our way.
I think because all of them would have a 2nd position that negates the negatives because they don't all have to stay forward during a match.