-
No because the brake cable is under tension and is raised off the tube by the stops so just cutting a bit of liner the exact length between cable stops for the inner cable to run through would be fine. The dynamo wire would also then not be attached to the tube itself, only running down the brake cable so I'm not sure if you'd consider it neater than taped to the underside of the tube but it would still be pretty neat.
-
I think it could look neater, but might take a little longer to set up, as apposed to the @spotter technique of the Di2 cable guides. Especially as I have a black cross check I just ordered a pack. Definitely an upgrade on my current taping job.
Seems like it would work. Maybe would need one or two bits of tape or glue to hold the liner to the top tube? Maybe not even if I used that really thin cable liner.