The issue with disc brakes is interference witht the fender stay: there is no straight-line route. My LBS bent the stays to route under the front caliper. You can cut, drill and form some metal to make a bracket to relocate a fender eyelet.
If your fenders are too wide for your front mech and casuing interference, you can remove some of the fender material. I use a dremel tool to chip away until the shape is correct (usually to produce a thin neck between the chainstays)