Cuckoo Marans, if you source from a good line with dark eggs, will produce Olive Egger sexlinks. With the Dominique, that rose comb combined with the genes for pea comb result in cushion combs. A Barred Rock crossing could yield a variety of shades, from teal blue to light olive green, and you would still retain the pea comb. If you used a Barred Holland, you would be sure of blue layers only.
From a production standpoint, the Barred Rock based sexlinks tend to be outstanding layers.
My boy had a red Easter Egger father, who happened to be pure for the blue egg gene; and a Barred Rock mother. His half sisters (same father, different mothers) eggs range from pale turquoise blue to a pale olive green.
Thanks! Barred Rocks will be easier to come by, too. I've got to look up what a cushion comb looks like.