Is there a way to create such a family?
More to the point, I'm trying to create a prestressed cable family, which goes through a beam on one face and comes out the other. I've already created a certain form of this using a face-based family, but that has many limitations. It only works on straight beams (on a curved beam it would keep going straight), the user needs to input the length value of the cable, etc. It has occurred to me to create a "Prestressed Concrete" beam family which comes with the cable contained within it. This would solve the curved beam issue and the length of the cable will automatically be the length of the beam. This might be a useful implementation, but it also has its limitations. Many times a cable doesn't run the full extent of the beam, coming out somewhere in the middle of the span. In such cases, the cable needs a special anchoring region which usually protrudes out of the face of the beam. Such a case would not be possible with a simple beam family (well, not without creating dozens of different family types for each beam cross-section).
So, is it possible to create such a thing as a beam-based generic family?