Well for those of us who are comfortable with a lightweight nerf gun, I think the crank could do. And batteries are bad fo' the environment foo'! (Unless you dispose of your batteries correctly, which I doubt happens with a lot of people)
You could modify this, Instead of having the mechanisms run by battery, you could run it by crank, no? Much like a gatling gun instead of a mini-gun. Would make it lighter, and you could probably make it stronger without having to worry about overworking the motor that drives the mechanism. Plus it would be much more intimidating (I think so, at least)