I don't see anything obvious. I know it's extra weight, but Johann is moving from a bowden tube to an on-hotend extruder drive for Kossel because of the quality of the print. It's a consideration. I asked him about it; here was his answer.
Quote
Johann
I think it's much easier to get retraction working perfectly without a long Bowden tube. My goal is awesome print quality without too much hassle and endless calibration. I'm still testing the effector-mounted micro extruder, but my first results are looking pretty good.