What a pity Pinion cannot be used with a mid-drive motor...
First let me say, that I do think the Pinion and especially the C1.9XR would be the best gearing system for an e-Bikes by far.
It combines all the benefits of an IGH like the Rohloff or Kindernay, with a comparable gear range, but with a more appropriate number of gears (14 is just too many for an e-Bike), and suspends the weight at the center of the bike.
As far as using it with a mid-drive it is totally feasible, all you need is separate drive chains for motor and pedaling.
The great benefit of separate drive chains is that you get the best of both worlds.
When using the bike with the throttle in motorcycle mode, you don’t have to bother with gears, and get the full benefit of a single gear electric motor.
When using pedal assist, you are not putting any extra strain on the pedaling drive train, so you can ultimately have a motor as powerful as you wish, without worrying about the pedaling drive train not taking the beating.
There has been two ways this is done:
1) Having a motor chain between the motor and the rear wheel, and a pedaling chain between the Pinion and the motor.
That was the solution taken by the early Neematic prototype, and made that bike the perfect combination of EMTB and light motorcycle, especially as they had also implemented a torque based pedal assist. Unfortunately after being acquired by UBCO, they dropped the pedaling drive train and made the bike a light motorcycle only.
https://lumberjac.com/2017/07/neematic-fr1-e-bike/
2) Having the Motor chain on the left side, and the pedaling chain on the right side.
That is the solution used on the two bikes below.
A) The LMX-64 which with a 2,500+W motor (with belt option), a regular derailleur on the right, and with Torque and speed sensor pedal assist in the pedaling BB. There is an owner thread on Endless-Sphere where users are raving about the solution the bike provide.
https://lmxbikes.com/en/all-terrain-emtbs/220-182-lmx-64H-enduro-emtb.html
B) The SEM Venom that uses a similar setup with a 4kW motor, but has not implemented pedal assist (although they could).
https://www.sem-e-mtbike.com/evolution/
Both the LMX and the SEM could implement a pinion gearbox instead of a derailleur in the bottom of their frame.
There is one catch however, and it is the Torque based sensing pedal assist.
Today these 3rd party sensors mostly exist as integrated in the Bottom Bracket, and so if you have a Pinion gearbox, you have no place to install one. There use to be a chain mounted system called the BEAMTS that is no longer available, and there is also a TMM4 torque plate that can be installed on the rear dropout, but is proprietary.
So at this point there is no clear solution for a good torque based pedal assist if you use a Pinion Gearbox, and that is the biggest issue (in my book).
But is someone was to solve that issue, or Pinion had the genius idea to integrate a sensor in their gearbox, it would allow for the perfect EMTB light motorcycle hybrid to be made 
www.pinkbike.com
