DoB

I've ridden electric bikes (both normal bike with a kit and purpose built Giant) looking at them for a friend with some mobility issues. From that experience:
I think your plan for an electric bike from a kit for occasional use won't work. The batteries and motor, even with NiMH batteries is going to add 40 to 60 pounds to your bike....which probably already weighs 30 pounds. I think once the gear is on, the bike will be far too cumbersome and tank like to run on human power alone. Two miles with any of these will be a workout with the motor off. Also, from my experience I found the bikes mass to affect them on bad pavement in a negative way. I can get my body off the seat for expansion joints and potholes, but these 70 to 90 pound bikes just seem to slam into every obstabcle in a jarring way.

I also looked at the Giant "Lite" which is about the lowest weight electric on the market at 50 pounds and costs about $1000. It is a comfort style bike with an upright position. The bike senses pedal effort and then the motor "helps" you along by assisting the cranks. The drive is through a Shimano 8 speed internal gear hub. I actually liked this bike a lot. It's fairly rideable with the motor off. With the motor on, you can bike along at about 15 mph while pedaling with what feels like about 10 mph worth of effort. You won't outrun anybody though....the motor phases out to zero assist as you reach 18 mph. I think this would be a perfect bike for an older person with arthritis or a bad back, or perhaps an obese person.

My regular bike with loaded (commuting) panniers is nowhere near as heavy as these bikes to start with. And if I was commuting on an e-bike I'd still need to carry the clothes and lunch I'm carrying now. I think they just don't have much advantage for anybody who is reasonably fit.