Sorry but I need control of both breaks independently on my mountain bike since I use one more or less depending on different circumstances. Maybe could be cool for a simplistic set up on a commuter or something like that though?

 I admire the creatvity, but using more of one brake than the other helps stop/slow down the bike better than using both brakes equally at the same time. Plus there are other reasons people use just one brake alone, like when slopestyle riders use the rear brake during a tailwhip wo help rotate the back end round.

 ewwwww, no hard feelings, but on a 2 wheeled ride, the brakes should be separated:-/
seems impossible to adjust the exact forces needed in different braking needs, on different terrain-conditions-speeds-whatsoever

props up for the idea though

 how would u control two brakes in one lever ????