I personally like Shaq with the starters. I think it maximizes his efficiency. A few years ago, I would've felt the opposite, as I think he could've carried the second unit. However, at this point, part of what makes him (and the starters) so darn effective is that you can't leave anyone alone.
I also worry about Baby and Shaq defensively. At least KG can help Shaq out defensively. But Shaq and Baby could be a problem.
However, if Shaq does go the bench, the return of West may help as he and Nate will help spread the floor and potentially open up things for Shaq, who would likely be playing even more against backup centers.