It seams to me the color would be the most challenging. I was thinking when I read this, would no black in the tails make them easier or harder?
It seams to be a challenge in wheaton varieties to get correctly marked tails in the females. I wonder if no black in the female tails is an advantage? I tend to think it is, because getting it right in these varieties (unless it is already well developed), is tough.
I have an interest in wheaton, not because I have birds that are wheaton, but most of the breeds that I have had or have had an interest in are wheaton based.
I looked at your breed's standard this morning, and noticed that lacing in the neck etc. is allowed. Is that a refinement that breeders of this variety actively pursue or not? These two points seam to add to the challenge.
Then I noticed that the under color should be slate. I did not expect that, but should not have surprised me. That must be for the male's color. I also noticed the requirements for the black in the wings. The first two breeds that I am interested in have a similar requirement with the wings, and these two points are part of the black balancing act. Neither of those should have a slate under color, but the tendency to have it is there. The tendency is linked to the quantity of black in the body color, and even linked to the intensity of leg color in my Catalanas. I wish the standard allowed for a little slate in the under color of the back in the Catalanas. That there is no allowance for it, makes the Black tailed Buff with slate legs a little more challenging. I am thinking that along the way, I will have to keep a reserve(s) of color (slate under color) on the side.