I was standing with a process engineer recently, looking at an operating paper machine.  On the floor, near us, was a complete doctor assembly that had been left out of the machine in a hurried press roll change.  Looking in the machine with a flashlight, one could easily see that this doctor was not optional.  I'll leave it at that.

Of course, no one should have left this assembly out, but let's not focus on that issue.  But now, both rolls of the press section will have to be removed just to install this much needed doctor.

Instead, just maybe, what if, a machine's components and frames were made with modern designs and materials.  Further, let's suppose such components as doctors and so forth were designed from the beginning so that they could be slipped in and out of the machine, en masse, so to speak, not dependent on removing any other items.

A lightweight design would give us room to do this. Lightweight components would not need fancy rigging to be slid into place.

Yet another reason to go lightweight and abandon the 1920's designs we often still see.