Robot rail with variable length

Hello,

I am trying to set up a linear axis for a robot in a library. The requirement is that I be able to change the length of the axis using a parameter or a joint.


Adjusting the length should also allow the robot’s possible travel range to change.
As a next step, up to four robots need be able to move along the axis.
I want to modify multiple instances of a resource reference in a library without having to create copies for each instance, because that would result in the copies also ending up in the library, which I want to avoid.
Has anyone implemented this before?
Thank you in advance