Actually it is possible to do by using formulas.
But it's a lot of work and not really worth the effort (except if you need it for movie rendering).
Faster and relatively easy to model, is using two telescopes for the upper and lower part of the cain.
And the arc-solid (turquoise colored), which simply travels half the driving-joint.
I should clarify that the picture I posted was only schematic and not the exact model I want to use. Therefore I think your solution is good enough.
However, I was kind of hoping I wouldn't have to do a telescope function. Instead I would of liked to build the cable chain inside PS and then scale the upper and lower part in positive and negative direction, while the arc is translated half the driving joint, like you suggest.
In our old simulation software the formula for a cable chain could look like this:
Scale (CoorsysOrientation 'X,Y,Z'): 1-dof(JointNumber)/(2*LengthOfChain)
Translate (CoorsysOrientation 'X,Y,Z'): dof(JointNumber)/2
Scale (CoorsysOrientation 'X,Y,Z'): 1+dof(JointNumber)/(2*LengthOfChain)
I'm afraid it will be too much work to do the telescope procedure for every axis on every robot.