I use path constraint with ChainScale a lot because it is very convenient to change the length of a path. However, ChainScale seems only work when Spacing is set to Percent with value > 0. This enforce the bones to have the same length which prevent me from optimize the number of bone. The common situation is, I prefer to put more bone on one end chat bend a lot and put larger bone on the other end as that side won't bend a lot. I suggest to make it possible to use the default proportion of the bones for scaling with the path when Percent is set to 0.

e.g.
Bone A: with length 100 will occupy 50% of the path
Bone B: with length 60 will occupy 30% of the path
Bone B: with length 40 will occupy 20% of the path