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. 

jagjag - An auto arm lifter (gentle) at the end of a record that does not thump the arm

My turntable sits within armreach of the main listening chair. The stylus never makes it past the first runout groove and is lifted. But if at the other side of the room......

@daveyf
I’d like to see an "affordable" tonearm that is able to do VTA on the FLY while the record plays ( the only way to do it so you can hear it).......and not lose its settings (VTF)

I believe of all the tonearms mentioned on this thread so far only one has this capability, and it is not the expensive VTA with remote control one that Larry mentioned. 8^0

Atmasphere ^^^ that is SOTA in my book. VTA on the FLY and not lose settings. A designer needs to think that VTF is important enough to make a design that gets over physics.

An uninterrupted run of internal wire from the cartridge tags to the RCA plugs.

No matter the design, it would have a removable head shell. Many companies now have that type as standard on their most expensive models.  There is not terchnical reason for not designing the arm with one, but old traditions die hard.

Every connection in a wire creates eddy currents and micro-arcing at the connection interface. This distortion is particularly harmful in a tone arm, owing to the fact the signal from the cartridge is the most highly amplified in all of audio. 
 

The same thing happens with physical vibration. Waves traveling up from the cartridge, instead of being uniformly and smoothly dissipated along the arm wand and into the body and base, are reflected back at the head shell/arm tube interface. Which is aggravated by the need for a fastening mechanism.

So it turns out there are a great many technical reasons why detachable headshells (and arm wands) are a bad idea. 
Unless of course you value being able to readily swap cartridges enough to make it worth the sonic sacrifice. In that case you really should just use a two or 3 arm table. But there’s always people who want to believe in the free lunch, a much more likely explanation as to why we see this obviously inferior design even on high end arms.