"....and since there are no body part "groups" in a rigged Max figure, this process is much more streamlined than the clumsy morph brush Poser Pro has."

Many Max users seem to assume that only Max can do certain things, or do certain things more efficiently than lower-end applications, which is usually untrue when you get down to it.

The Poser morphbrush works from parents to childs.
I.e.-you start with a deformation on the parent so that the vertices located on the seam will be included.
Then you just go on working on the adjacent child bodypart.
This makes it pretty easy to work across seams on a "live" (i.e. grouped) Poser figure.

But if you need to really smooth a mesh across the seams, import it with groups welded, do your morphbrush work, then export the finished mesh while welding it, re-arrange vertex count, and Bob's yer uncle.
I do that almost daily and the import/rearrange takes about a minute or two of extra time.
It's not a morphbrush problem, but a grouping problem.
You have to do exacly the same in ZBrush, and I doubt MAX can smooth/morph across seams on a grouped (=cut into separate bodyparts) mesh.

In other words: Poser 7 or Pro can rig a mesh towards the same standards than MAX or any other high end app using weightmapping others can do. Period.
It may take a few minutes longer, but the tools are out there.