It would depend on how the joints where going to work. If the armor was going to be light and form-fitting like the StarWars white stormtroopers, I'd use a catsuit (black) and build the armor as props then parent them to the appropriate body parts on the catsuit. You could then conform the catsuit. If the armor was going to be heavy and the joints where going to part of the armor, I'd probably use a figure just for scaling while building the mesh and convert the mesh to a figure. Assuming that you'd only be seeing the head of the Poser figure, I wouldn't even try getting the armor to work with the figure. I'd just use the head of the Poser figure and use a neck collar to hide from the neck down.