If you were to design a tone arm, what would it look like and feature?

Just a thought and I will take this up with my son in law to be an industrial robotics engineer. Robots have gotten accurate beyond belief with motors and drive systems accurate to less than a thousandth of an inch. It should be possible I would think to watch the groove with an optical sensor and drive a tangential tonearm accordingly. This would be far more robust than whisker contacts. 
He will be home from China in 10 days and we will see if that idea is feasible given current technology. 

I like the Reed arms. They meet all of my requirements. The T5 is a bit over the edge. It is very complicated for minimal return if any. But, I have not seen or listened to one so I really have to reserve comment. In the world of mechanical devices simplest is usually best. 

Millercarbon, it is Frank Schroder. Frank and Peter are in bed together (imagine that!). Frank's tonearms are very interesting and creative. I personally would never buy one. Like Unipivots his designs are a way of avoiding the precision of aligning bearings correctly the result being too many degrees of freedom and variables that are difficult to control. Frank Kuzma's  4 point design is far more elegant controlling all unwanted motions with the lowest amount of friction in an easy to build format. 
Daveyf, you are far too polite. Anyway, I would take the 4 point 14 and try to lighten the effective mass getting it down to 14 grams by using carbon fiber so that people with medium compliance cartridges ( the vast majority) could enjoy the use of a 14" tonearm.