Same here I just buy from different hatcheries to get a mix of genes and then cull to move toward the ideal chicken for various attributes.
I'm not much interested in the SOP for 'show' since I don't plan to show birds. Like I'm actually not keen toward huge birds so size is not an attribute I cull for. Personality, tameness, overall health, athletic prowess and good posture and pretty feathers are all things I work toward.
I like broody chickens because they not only tend to protect the eggs but they also tend to adopt and protect the younger chicks if you watch them. I also like "alpha" pecking order birds and I prefer birds that are tame toward humans (hunker down when approached) but aggressive toward predators do the ruffled neck feathers thing
I don't mean to sound snobby here as I am also new to chickens but not new to breeding. One of the great attributes to giants is their size and good attitude from the one I have and from all that I have read about them. If you don't like the size then why choose this breed? Whether someone shows or not, the decline of any breed is NOT breeding to the standard. I'm sure if you asked any chicken breeder, they would probably tell you that only a very small percentage actually show well but they continue to strive to the SOP as ANY breeder should. Anyone who breeds a heritage bird should always try and breed to the SOP. It's what keeps the birds we all like so well, true to form and character.