I’ll play devils advocate here. The reason cable runs have stops on the frame is that the cables need to be held in tension, and the very best way of doing that is to secure them against the frame. Full length outers may seem like a plan, but eventually dirt will get in, and then your shifting will be worse. it’ll wear out your mechs and shifters quicker, and you’ll get through more outer making your shifts less crisp. Even an XTR complete cable kit (outers inners, and so on) is only £15.00. Change it all once a year. Jobs a good un.
If full length runs were such a good idea, bikes would come like that, no?