OK, so Muddy's coat is his flaw. Is he a stable dog otherwise? You probably show them, so is he, outside of his coat, a good example of the Weimaraner breed?
Personally I wouldn't breed a longer coated weim if I was looking to breed dogs for conformation, because according to breed clubs, their coat should be short and smooth.
BUT, if I was breeding working dogs, focusing mainly on temperament and drive, I wouldn't think twice about breeding a superb working dog with a conformational flaw like a longer coat.