linebreeding is actually the "quick-fix", it would take much longer with only very carefully selected outcrosses... lifetimes perhaps, depending how refined you want to goThat low a percentage just wouldn't warrant the years of line breeding.
the outcross is the "finished product"The idea is to fix traits and every outcross adds 50% new genes to the mix and negates the linebreeding until the offspring can be bred back and reset them. EVERY outcross will do this.
That really is the best way to view it, from a breeder's standpoint. But only considering that you already have in your lines the best possible breeding stock to work with. If you are satisfied with 70-80% of what you produce, and feel there's no need for improvement, then linebreeding with occasional type-to-type outcrossing (from a similar genetic population/ancestry) is all you need to maintain this. Linebreeding near the founding times of the GSD, was in a way a necessity, to establish a consistent type for the breed. As mentioned before, those percentage figures are really subjective, in that they are depending on what you're original breeding stock consisted of, and the goals or satisfaction level you seek. If you start with less than ideal material to work with, then maximizing for hybrid vigor is the aproach you may want, then refine.I view linebreeding solely as a tool that produce consistency in a line