derailleur

Anything else that doesn't actually bend the derailleur is a non issue.

Will widespread adoption of this device encourage development of a front derailleur that can handle more than three rings?

A well-maintained derailleur system is very light and very efficient, and with a bit of practice, easy to use.

He had grown up close to the mountains and all bicycles sold there have Derailleur gears.

If your current wheel is a free-wheel (not cassette), then you may require minor derailleur adjustment.

Ah yes, the derailleur thing sounds like the real issue that internal gearing aims to fix.

Well, some of these guys are also riding single-speed fixies over a century after the invention of the derailleur and freewheel.

Even found a banged up old bike (dead tires, bad derailleur/gears) laying in a gutter.

A planetary mechanism built inside the rear freehub provides clean and reliable gearing, albeit at a slight efficiency loss versus derailleur gearing.

Aside: I'd have fixed or replaced the derailleur too, and I'm not that short of funds.

And the derailleur specs are wrong too (BikePedia has the right ones).

I’ll strongly advise against a conventional derailleur with a mid-drive motor: the derailleur needs a thinner chain which wear faster, especially with a motor that apply more torque than a normal human.

"Light and compact – much less than 1kg weight and 20mm width." A front derailleur typically weigh 50-100grams.

:) Adjusting the derailleur can help; in particular the "B tension" adjustment to get the jockey wheel to track the gear cluster more closely for more wrap.