I've ridden a townie before & I don't disagree with you. Reasoning behind the BBSHD is not to optimize it's capabilities necessarily but if I'm going to invest in a build then as the saying goes "better to have it & not need it than need it & not have it". Besides 20mph is the legal limit & I'm good with that. Even at 20mph I'm going to have to be extremely lucky not to ruin my day, maybe even a week or month, if I biff. I've had a front blow out before coming down a hill in a turn. Fortunately I was young & could jump tall buildings at the time, still lost my shirt & half my shorts, lol good times.
To clarify I'm not looking for a whole bike necessarily. Just a frame as I don't need the rest, I've got that. But it does have to be some form of flat foot cruiser design that will allow the addition of rear gearing etc. as mentioned above. I checked out bikesdirect but they didn't have any geared cruisers that appealed to me. I'm trying to find out if gearing & disk brakes can be added to a single speed frame but I wouldn't think there's room. A Townie 7D is $500. plus not including tax and in my neighborhood if you can find a second hand one they're asking almost as much. I don't see the value of paying that when everything but the frame is useless to me, $2-300. maybe.