I like the idea of Pierce in the Hondo/Ginobili 6th man role. I've actually been in favor of it since '08, given a solid enough SF to start in his place (Posey then, Green now). It just makes too much sense.
1) It is difficult for all of Pierce, KG and Allen to get off offensively at the same time. And of the 3, Pierce is the one whose production relies the least on Rondo and who makes the most sense as the engine of the second unit.
2) The defining difference between the Celtics and Heat this year was that the Heat are younger. No other way to put it. They could turn it up, then keep it there for 48 minutes with LeBron and/or Wade going all out all game. The Celtics could match that for awhile, but the give-back when a LeBron or Wade-led second unit faced our unit without either KG or Paul on the floor was too large AND by the end the Celtics were just exhausted. Pierce coming in fresh for the second unit and then finishing the game relieves those issues.
3) You have to maximize your resources. And coming off the bench doesn't suit Green's strengths. He's not a create-your-own-shot scorer, he's not an instant-offense shooter, and he's not an energy guy. What he is is a 6-9 athlete that has a decent set-shot, is a decent passer, is good at running the floor, and has the tools to be a solid role-player team-defender. In short, he actually fits in perfect in a glue-guy role next to Rondo, Allen and KG. This lets Rondo be even more of the floor general to start the game, with natural 2-man game partners at the other 3 starting scoring options.
Honestly, this idea makes too much sense to me. I don't know that it'll happen because of Pierce's identity as the captain and longest tenured Celtic, but strategically I think it's the way to go. And if there's any franchise in which a 6th man is honored and known as the weapon it could be, it's the Celtics.