You mean something like this im guessing
Pros
Easy to fit batteries and motor as it is not a cradle type frame.
Looks to be belt drive, which makes for a very silent ride, especially if u use a brushless motor
Cons
Batteries not hidden behind a fairing (bad aesthetics in my opinion)
Doesnt look like a very aerodynamic bike, which will reduce range and top speed
But this all depends on your intended use, if you just want a cheap inner city commuter this would be a good choice as the aeros mainly come into play above 70kmhr, and the lack of fairing would probably allow more batteries for extra range (if the bike can take the weight of course)