I hope this idea catches on. Marquis doesn't necessarily replace Ray, but he can provide a boost to aging starting lineup. He can be the lockdown defender thus it allows Pierce to save his energy defensively. And Rondo get a running-mate on fast breaks. Doubt Doc can pull this off. He can't even reduce lazy Sheed minutes. Being a players coach has its downfall.
I think you're overestimating Marquis' impact. While younger than Ray, he hasn't made much of an athletic impact. He doesn't exactly fly on the break, nor is he much more of a threat than Ray off the dribble.
He's a nice safe option who makes the right decision more often than not, but he doesn't add anything to the starting unit other than more energetic defense at the 2.
I'd rather start TA than Marquis if I was looking for athletic impact with the starters. His rebounding, ballhawking and attack mentality would at least shake things up.
Neither of them should be starting over Ray at this point, IMHO.