What you say here makes perfect sense.....however no judge can evaluate a "line" of dogs. That is the breeders job. The judge can only look at 1 dog at a time. He has no way of knowing the quality behind that dog.
In many, many breeds when you look at the pedigree you will see that quite a few of the females used in the breeding program are not champions. They may be pointed perhaps. But when you have a breed such as Collies, or Huskies, or anything else with hair, very often they blow coat when they go into heat, and it takes 6 months to get a decent coat grown back.....just in time for another heat
The proof of a dog's quality is in what they produce. If you know your bloodlines, then you have a point of reference for what you can expect to get out of a dog, or a pair of dogs.
The maximum weight for Chis is 6 pounds I seem to recall. I would feel more comfortable (now, this is me personally) not breeding a bitch that weighs less then 8-ish pounds.....as long as I knew she threw SMALL.
That is where the little males that throw REALLY small come in--no pun intended there. And if it is a line breeding then you can very often predict exactly what you should end up with. Of course when breeding you can never be 100% sure. There is always mother nature to contend with, and her sick warped sense of humor.