Old thread, but I used it as a reference, so wanted to chime in my results.
I used Problem Solver stick on cable guides for my external RS Reverb routing. The hose was cut for a previous bike, so routing along the rear brake cable wasn't an option. I'm happy with how it turned out.
$11 for a pack of 5 stick-on cable guides (only needed three) was cheaper & easier than a new control hose.
No pics as I'm away but cable tied to the brake hose like Muzzanic did then vertically up to the post (Thomson Elite Dropper). I found this looked the neatest route without resorting to sticky cable guides