I have the OBS and have the 2nd element added and don't need to worry about adding any bricks etc for heat mass and don't need to worry about losing the extra heat from the generator. When I built my Habitat for the Bradley, I designed it to permanently have the cold smoke set-up and to use for both hot and cold smokes. I decided not to permanently run it that way for a couple of reasons.
When I do an overnight smoke I substitute a larger pan of water to catch the pucks and drippings.I have the Bradley cold smoke kit and it doesn't accommodate a larger pan so you would have to watch it more when using a lot of pucks. A custom made cold smoke box would solve that problem. The other issue is with the OBS sometimes the pucks are not as fully burned when cold smoking as with hot smoking. Might be the additional heat that the puck gets from the element (just guessing). Since I hot smoke more than cold smoke, I didn't want to waste the pucks.
So my design allows me to do either. When I hot smoke I disconnect the cold smoke box (with the hose still attached to the box) from the cabinent and store underneath). It is not much of a pain to switch, but then again I don't switch between the 2 methods that often. But iif Ii did it still would be pretty easy to do. (a link to my setup -http://forum.bradleysmoker.com/index.php?topic=16087.0)