Line breeding itself is not inherently bad. Its the goal of the linebreeding and the individuals that you linebreed on that can cause issues.
If your line breeding for pigment or toplines as opposed to workability then you get what you get. Then again if your outcrossing for those same traits I dont see you being much better off.
Such shy animals are in all circumstances an encumbrance to their owner, who must be ashamed of such a dog, and a disgrace to their race. Under no circumstances whatever must they be used for breeding, however noble and striking they may appear.