Crabbe is no better defensively than C.J. If you start Crabbe, Dame is your ONLY ball handler. That makes it to easy for other teams to shut down our offense by trapping Dame.
Turner addresses the ball handling issue, and is a better defender than Crabbe or C.J., but now you have an offense that relies on spacing and outside shooting with three guys who can't shoot (Plumlee, Davis/Aminu and Turner). Maurice Harkless is a borderline 3rd option. No way can we succeed with him as our second option on offense.
Dame/C.J. may not be perfect, but they are light years better than any of these other proposed combos.
Crabbe is way too one dimensional, can't create his own shot, or for others. He needs to be on the court with at least two other ball handlers to be effective.
Turner can't shoot, so he needs to be on the court with at least two other great shooters to be effective.
Let's face it, with the players we have, juggling our starting back court is equivalent to rearranging the deck chairs on the Titanic.
BNM