I imported eggs from Germany Holland Japan and France during the 80's. Very few eggs ever hatched. It was a waste of time and money. I have imported many breeds of chickens in the past 30 years. I must say that the american bloodlines have been mostly superior to the european and british ones.
Light breed chickens range far. The heavy breeds dont stray far from the chicken coop. Lakenvelders and Hamburgs stray far and lay their eggs far from the coop.
I trust my most valuable hatching eggs to dark cornish game hens and aseels. They usually hatch a better percentage than an incubator. In addition if your electricity stays off for hours you will be screwed. They protect the chicks from small predators and allow the baby chicks to eat grass...
Maybe you should consider black minorcas and dark cornish. The minorcas and cornish will forage for most of their food. The cornish are wonderful mothers that will replenish your chicken supply. Hawks will catch any free ranging white chicken.
Many of my rare breeds are inbred. Brother sister is the closest you can inbreed. Sometimes it makes the birds grow slower. My Yamato, Chu-Shamo, Satsumadori, Kimpa, Ko-Shamo Chibi, and O-Shamo are inbred to differing degrees. Some are losing some body size as a result. Its a good way to clean...