The Bafang BBS02 came with (because I added it to the order) what looks like a genuine shift (“gear”) sensor made by the original company in the Czech Republic:
On a typical bike, it mounts against a cable stop with the cable housing holding it in place against its other end:
The Terry Symmetry has only two lengths of housing: in front of the adjuster on the downtube and behind the stop brazed to the chainstay. In either position, the sensor would move as the shift cable flexed and (IMO) put unreasonable stress on the electrical cable running to the motor.
Yes, the Tour Easy has those same two lengths of housing, but the forward one joins a sheaf of wires & cables that barely moves.
Fortunately, the sensor fits neatly between stations 1 and 2 along the downtube, with a snippet of PTFE lIned housing holding it firmly in place, with the 3D printed battery mounting blocks including paths for both cables:
The shift cable originally ran from the adjuster in the front to the guide under the bottom bracket along a slightly diagonal path I could not possibly match. Instead, the path is now parallel to the downtube from the front adjuster:
.. to the rear block, where it angles downward over the motor to the bottom bracket:
The front block at station 1 has a Delrin / acetal bushing to align the cable with the rest of the blocks:
Yes, it’s a round peg jammed in a hexagonal hole:
Turning it from stock is well within the capabilities of Tiny Lathe™:
For great slippery, a similar UHMW PE bushing supports the cable bend at the rear of the station 4 block:
The Basement Laboratory Warehouse Wing disgorged an overly large rod taxing Tiny Lathe™ to its limit:
Memo to Self: next time, just saw off a stub and move on.
The Smell of Molten Projects in the Morning 
I hope this isn’t one of those projects where you say, “You buy the parts and I’ll install them for you some afternoon.”
I know myself better than that! [grin]
The big question: would the battery fit anywhere on the downtube?
After that, it was just pleasant problem-solving, solid modeling, and routine 3D printing, the kind of thing you can’t do when driven by either (or both) schedule or profit.
Ed didn’t say that exactly…. but pretty close.