Why does everyone think this is a great idea? If his performance over the past few seasons is any indicator how his game would complement the Celtics, why even bother?
Theoretically, we could move House to the 2 where he's better suited (not necessarily defensively though, as he's certain to continue getting burned even as a 2) while Marbury handles the ball... but that whole theory lies under the assumption that Marbury would defer to the team game.
Forgive me for having doubts specifically about Marbury's willingness to "buy" in. Another thing - his game has always been more suited to play the Rucker Park type ball. If you are ready for lots of crossover dribbles and forced up shots that appear drawn out of an and-1 tourney than an NBA playbook, be my guest, have your Marbury. I think if Marbury becomes a key part of the rotation, it'll be a disaster warning. We won't perform any better than we did during this road trip. He'll stagnate the second unit even more than it's already been doing on its own.