Road levers all seem to be a wide U made of bent plate, whereas MTB or BMX levers are pretty much all a thick casting or forging... you'd need spacers, I suppose.

Come to think of it, it would interfere with the mounting on pretty much all of the levers I've seen... and if you tried it on an aero lever with mounting separate from the pivot, you'd find a projection between the sides of the U. Prolly take an unfeasibly large amount of fettling.