The problem with the curve nodes is that they require a special user interface that Poser doesn't have at this moment.  I have made a simple replacement material for the missing Cycles Color Ramp which you can find in the free stuff section.  Look for 7 color color ramp. At the moment it only does constant and linear, however you can change types with-in the node.  So part can be linear and other areas constant.  I am working on an improved version that will add in the Ease and the HSV color hue shifts.  The ease was a simple addition.  The Color hue is giving problems as it crosses the Zero point.  Should hopefully have that solved soon.

The biggest problem with the user interface is that each node is fixed in size for inputs.  Whereas the Cycles Color Ramp allows you to add dozens of points and slide them back and forth.  That by itself should give an understanding of how hard it will be to put that node with that functionality into the material room

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13