Hmm
I can see where you are going with this.
Re the J shaped tube I still think that a tube with a flared trumpet shaped mouth (Shaped exactly like the inner curve of the hooked part of the J) would give you the same degree of control without the need for extra motoring or even castoring (same effect but unmotorized and therefore simpler).
The electro gripper as a way of starting off though is clever.
As for finishing. two turns round a post and then forcing the wire into a 'V' shaped cutting blade (A bit like IDC) made from two sharp blades clamped together should do the trick. It's all in the angle of the V. I guess it could be mechanized with a solenoid too after winding one.
I guess with the two turns round the post I am thinking of potentially going straight into a second or third or further number of coils without actually stopping.
If the former is tall enough and built correctly you can coil a whole bunch of separate coils separated vertically starting and ending with a turn round a post before finally cutting at the end of the last coil.
The coils can then be tied/taped off one at a time and the leads cut at the post before lifting each one off the former.
An adjustable former would probably be a good idea too.
I watched a couple of old guys doing rewinds at a company I worked for. the former they used had four posts each of a suitable diameter to avoid upsetting the minimum bending radius of a theoretically worst case wire size.
Each post was adjustable in/out down a slot angled so that the coil shape/size could be largely approximated. Final coil shaping was done at the time the coil was inserted into the slots in the motor. It couldn't be tightened up and taped before or it wouldn't fit through the narrow part in the top of the motor slot. (Clever eh, I always wondered how they did it until I saw)
If an adjustable former was made in a similar way but with 8 posts/slots and included your idea of a start gripper with a useful narrow diameter post for intermediate starts and finishes. (Good for constructing coils with multiple taps too) Together with a V cutter. You should actually be able to achieve most tasks. Including winding more than one coil at time.
Thoughts for what they are worth
aka47
Necessity hopefully becomes the absentee parent of successfully invented children.