re AEO
you're probably thinking of shimano 'link wire' style straddles, where one side is a housing of fixed length and the brake cable runs down it to one arm. older style yoke carriers use a second wire for the straddle, and the brake line terminates at the carrier in the center, this means you can have a barrel adjuster on the horizontal straddle wire and let any changes in length freely slide between the left and right arms.

having a variable length horizontal straddle wire is important for me because:
consider as pads wear down the distance to rim increases, typially we compensate for this by adjusting the barrel adjuster on the brake lever (at handlebar), this decreases the distane but also moves the pivot point of the straddle wire higher, resulting is less mechanical advantage
a better solution is the have a barrel adjuster on the transverse cable, this directly pulls the arms in closer, but the pivot point stays at the same height, thus the same leverage is preserved throughout pad life

a number of expensive brakes use this mechanism... but most don't meet all the other requirements in my list or have some other flaw...

re: fietsbob
the Paul touring canti is close to what I want, except the cable anchor doesn't pivot
i should also clarify that i don't like the type of springs it uses, i'm looking for the type with a hex bolt adjuster on the side as found in most common v-brakes



The Avid Shorty Ultimate Cantileveris close to what i want, (AEO: note the barrel adjuster at the tip of one arm) however it's flaw is that it has a 'folding' gimmik where the arms can be folded to either a wide profile or medium profile brake, which I just don't trust, also it has the inconvenient frontside adjustment springs

Thanks for suggestions so far