The motor kit I am using is 300 watt (no Motorscooter license req'd over here) and fits at the crank. So rear gears ( 7-8 speed) are still available and all you need to be honest. Assisted range is about 60-70 km, depends a wee bit on hills obviously but I rode up a reasonably steep hill for about 600 meters sitting down at about 15 kph and didn't even breathe hard. A charge would cost about 20c - 50c depending on provider and 80% of NZ's power is renewable Hydro so a very small eco effect.
Auckland has a lot of cycleways already and lots more coming and I see a lot of riders on my trip to work each morning, mostly without motors. Potential customers !!
Alex, I think mobility scooters, the 4 wheel kind, have already taken that market.