I think the Celtics will play some zone with their second unit so that Shaq doesn't get exposed in the pick and roll. This means that a shorter/weaker 3 like Wafer is less likely to get exposed in the post, where he is most vulnerable.
That's a good point. I think they already do play pretty much a matchup zone, but they probably will adjust it when Shaq is in there, probably setting up something where he and the other big man are constantly switching, so the other guy is always the one blitzing the perimeter, while Shaq stays either on the backside, or in the lane.
But with a front line that includes Shaq, JO, KG, and potentially Perk, I don't think many teams are going to be able to do too much work in the post with their SF's. The help defense will be too good, and the paint will be too clogged.