Dark brahmas aren't laced at all. Lacing is black edging (or blue/splash as it's a dilution of the same gene) on the feather. Dark brahmas have the ground color around the edge of the feather making it penciled. I don't know enough about the genetics of crossbreeding, but moving the black from the edge to a line in the interior of a feather I suspect is NOT easy.
Wikipedia
There has been controversy and confusion over the origin of the Brahma. It appears to have developed in the United States from large birds, with heavily feathered legs, imported in the 1840s from the Chinese port of Shanghai, and thus known as "Shanghai" birds.[4]: 78 The distinctive head shape and pea comb of the Brahma probably result from cross-breeding with Grey Chittagong birds of Malay type, imported from Chittagong in eastern Bengal (now Bangladesh); these characteristics distinguish the Brahma from the Cochin, which also derives from "Shanghai" birds.[5]
In looking up the chittagong chicken, I found this:
https://cs-tf.com/malay-chicken/
That comb, and height crossed with a cochin, with more back breeding could easily get the Brahmas. The statuesque body shape of the malay with the bulk and feathered feet of the cochin. The wyandotte has a rose comb which CANNOT make a pea comb at all. Both are equally dominant and when both genes are present, you get a walnut comb (like a pure silkie). When only one is present, you get the comb type showing, and when neither is present, you get a straight comb.
Going back to the pullet age, I can see both
View attachment 4011972View attachment 4011973View attachment 4011974View attachment 4011975View attachment 4011976View attachment 4011977the straight back and long legs: Malay
The short neck, super fluffy but and broad back: cochin
Both cochin and Malay have enough feather varieties to get to the desired colors without stepping outside of either breed.