I don't have a white lab coat!
(I envy your technical expertise Si)
But since last June I learnt a lot about riding a pedelec and building in the right components and have my method for smooth starting and general good riding experience:
1. always use the right gear (yes even with a hub motor this is important) I have learnt to change down in time which is very important and use the correct gear when cruising along.
2. this means having the right gearing on the bike - I understand your initial concerns about my build now d8veh!
I have moved from a 42 front cog to 48 and my next build will be at least 50.
3. use the correct assistance level - if you are going to power away from a red light in level 5 prepare yourself for the 450 W!
4. have the right controller and PAS - since I changed to a 12 magnet disk there is a light year of difference in smooth operation. If you are using a 6 magnet disk with a square wave controller of course PAS is going to be cr@ppy! The above 450 W and associated torque kick in after a quarter turn of the crank. I have yet to be beaten from the lights to 10 km/h by a car, by a motorbike yes. Acceleration is not off/on but smooth and regular up to the aforementioned 10 km/h.
I believe you when you say that a torque sensor is more natural, I understand the physics, but I don't have the extra cash to go down that road myself. I will have to arrange a road test at the LBS to see for myself. A day he is in a good mood because he knows I am not a potential client for a factory built bike.