Hey Greg,
I too have considered doing some custom BH builds, but in addition to the reasons that Hans bings up, there is always that little maxim of business that can put a real damper on things -- the customer is always right.
Even selling used gear on audiogon and other places, this has bitten me in the butt in some completely irrational and wholly fabricated ways.
I'll do if for friends and relatives but as much as I'd love to put together some sonically and aesthetically superb systems for some folks, even on a very limited basis, I really don't want to ge burned by some idiot who has a bad day or just feels like making trouble.
You could build on spec and sell on audiogon or whatever and that may be a bit safer than contract builds. May.
-- Jim