Two levers, one calliper - Extension/Interrupter/Cross Levers

Sheet, I only just saw a brake "lever" that does this, its a single handlebar mount that sit's near the stem, with two levers, one for each side and they both pull the same cable, specially designed for safety-conscious fixsters....think it was dia compe.

but yes, cross bikes have two levers which both pull the same brake, so it can be done.....not sure if there is two inners in one outer, or two independent cables, think it is the former.

One inner, outer slightly longer and cut in two to insert cross lever. (The cross lever pushes the cable outer down, rather than pulling the inner up, which is why it's a bit spongey).