Yeah that's right, I'm interested in weighting the stiffness of spline dynamics, not joints. So one point at the end is totally rigid, the next couple are some what rigid etc etc until you reach a point where the spline flops around freely, something like how a cable would behave. I have found I can use multiple hair constraints to achieve this but its not the cleanest setup. In the hair constraint tag there is a slot here
for influence map but I don't know how to make a map that will go in there. Vertex doesn't seem to work with splines.