The cables have been crossed on my wife's Erickson since Glenn E. assembled that bike in 1997. The cables have never worn where they cross. I've been doing that on my own bikes (where it works) since 2003 with no ill effects and the benefit of smoother cable housing past the head tube, notably with no marring of the HT finish. There's no evidence of higher friction while shifting. I do add a small length of clear tape on the underside of the DT where the cables come closest, but there's no actually rubbing there. OTOH, if the cables normally would be in contact with a frame tube, I wouldn't do it on such a frame.