I investigated the double brake possibility for the same reasons as you and i just wound up running a hood and a dummy hood (They are that awesome and cheap Campy Ergo copy made by Tektro). I have never once grabbed the dummy lever wishing for a brake, but I had already sort of trained myself to use only the front brake in panic situations.

If you have a nice low gear you will be braking with your legs mostly anyhow so all this cable related head scratching and gadgetry will be moot.

One things for sure, anything is preferable to road bars with one aero lever.