O-R,
I asked the same thing about glass slides, and was told in no uncertain terms by everyone to leave well enough alone. I took one apart to see if it could be done, and actually it does look to be a rather easy exercise, but whether it would work afterwards is another thing. The slide I worked on by the way is still working fine.
Now when it comes to Newall equipment, you are talking about a totally different bit of kit.
They are one of the world leaders in this technology, and you are perfectly correct in that some of their read heads work by using balls as a datum reference. But you must realise that they are designed so that they can actually work underwater, so any breaking of seals might cause problems. In fact, by the precision they can work at, I would suspect that the units are assembled and sealed in a cleanroom environment, and I would imagine taking a hacksaw to them wouldn't do them any good.
Also to be considered is the cost of the readout to go with it, if it is the ball type, you could most probably buy a full glass scale setup, or even a couple of setups, for the cost of just the Newall display to match the read head you are on about.
Bogs