I agree with Vskid... Don't worry too much about regen, just get some extra range. Even a 500W motor is plenty. That's more than Lance Armstrong could crank out, and you will be adding your own muscle power to it.
Personally I don't think a front or a rear suspension is necessary.
Here's the kit that MMM recommends:
http://www.amazon.com/gp/product/B00GIXZKP8/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&cre ativeASIN=B00GIXZKP8&linkCode=as2&tag=lifereeng-20&linkId=74ABSSZGKT2WHZ6O
It looks like there are 7 speeds or "cogs" on that wheel? You need to be a little cautious to make sure the chain is the right thickness. So I would look for a bike that also had 7 cogs and disc brakes on the back wheel. However, some of the questions say it will work even for single-speed bikes.