Hey Leo, I don't understand your logic. I believe that besides a dual brake lever having a low safety factor based on what I'd described earlier, it will actually give you less control over your braking needs. In fact, just the opposite of what you stated is true: you can apply about twice the braking-force with two hands than you can with one, plus you have the safety of redundancy if there's a failure on either. I strongly advise anyone to avoid a dual-cable brake-lever for safety's sake.
Do you have a link for this brake/clutch lever? I'm having difficulty imagining how that might operate.