Interesting idea....would probably work too...of course taking the lazy way out maybe we could mod the engine for more power...Oh yeah!.....I did see a story on a fella named Dr. Abbott I think years ago....had a 20" bike (well wheels at least)....and had this humongous (I think 140 tooth or so nut it has been years since I read about it) front chain ring and went something like 120 MPH or so with human power only on the flat...of course he did cheat a little and had a specially designed vehicle break the wind for him (he rode behind the vehicle in an enclosed area behind the vehicle).
I'm not truely concerned about how much power I will add to moving the trike. It's more of a thing of during my 50+ mile round trip commute, I might as well get some exercize. And if I'm going to pedal, I'd like to be able to keep up with the motor. But I think 140 tooth is a bit much.
I bought and installed a 62 tooth. Unfortunately, I had to change my freewheel cassette to a 7-speed which has a 13 tooth high gear iinstead of the 11 tooth I had on the old 8-speed. Compromises. Oh well.
Heck with your bike not needing a pedal assist when starting off as seen in your amazing video's then it would look so cool pedaling up a steep hill with that crazy gearing.
But then again,it may be a real dawg in the event of a minor breakdown where you need to disconnect your chain so you can peddle on home.
I say as long as you can keep up to 30 mph you should be okay.
I'd really like to know what size front sprockets would be needed to assist a motor.
My pedal gearing is at 36t in front & 16t in rear, and it sucks regardless of the engine being on or not. I went ahead and bought a new 44t crank but haven't installed it yet. I'd much rather wait for something between 50t & 60t crank. My local bicycle shop prolly lied when they said 44t was the biggest available.
I can pretty easily pedal up to about 25 mph in high gear. As for pedaling if the motor breaks, I've had a couple of electrical glitches (under control now). I've had to pedal home 7 miles over some pretty steep hills. My low gear is 27t on the front and 34t on the rear. With a 20" wheel. It can take a while to get up a hill, but it will get there.