Does it stop them working not being beauty queens? I wouldnt have thought so, so what would be the problem from breeding from a good working terrier that was a bucked tooth monster as you said?
I think the best litter of pups worth being proud of would be the litter that has the best chance of becoming decent honest workers. Got nothing to do with looks. Looks shouldnt really come into the equation if you are just want a working terrier
To answer your question, yes i would have an ugly terrier from a litter if it meant it had a better line of workers behind it than say a good looking p