It wouldn't offer any advantage, the force requires to shift a hub isn't enough compress a standard Bowden cable by any significant amount and the mechanism doesn't require the same precision as a derailleur. If it was better, then standard gear cable would be specified, compressionless brake cable is basically the same, with a strengthened sheath, of Kevlar or similar, to stop the inner bursting out under force that brakes require.
Are you dissatisfied wit the way it currently shifts? Friction is the enemy of good shifting on a Rohloff, good inners, clean outers, sweeping bends, all contribute to a smooth sift. My Airnmal folder, with a less than ideal cable run, takes a firmer twist to shift.