Half the problem is we're losing games becasue we're exhausted. Doc's driving these guys into the ground. I like your idea about mixing it up like Phil Jackson did alot. It's becasue Phil has very little fear a coach. He has no problem trying "anything" that might possibly work or shock the stagnant play.
So to me playing guys who have sat and not produced or sticking with guys who have played and not produced or simply playing 6 guys into the ground and losing cuase your toast is all 1/2 dozen or six of another to me.
Whatever I did, I'd try to do it early and whoever I used the primary goal would be to get each starter ( esp. Rondo with his ankles, Ray and Paul; Baby and Perk are younger) at least 10 minutes rest heading into the fourth.
Pruitt proved very little this season. But one thing he did prove is that he plays some pretty sticky defense. He has some length and even played some pretty good D on Deron Willaims among others. He moves his feet. Tell him to deny whoever he's got and on offense just make the safe pass and move with purpose on the sets, don't try anything special.
Ultimately as others have mentioned though, you'd rather Marbury or Eddie...but if they're doing jack....what have you got to lose? maybe you gain.