I have a Blue Exchequer Japanese bantam hen.
I'm still going to do some experiments to see if I get the same results with other birds.
Have any breed ideas I should cross either Squeakers, or Bigfoot too?
I'd be curious to see the results of the experiments.
Crossing: If you just want to test whether their mottling is the usual recessive, or an unusual dominant form, then cross to birds that are not-mottled and not-white, and see if you get any kind of mottling on the chicks.
For any other purpose, which ones to cross depends on what results you want. You could get interesting chicks from any of those females.