I understand that brine shrimp are living fossils... I deal with them all the time. And I'm with you on the body plan discusiion, and the significance of turning off genes for extra limbs. OK there.
But I don't believe it's splitting hairs to say that your "ancestral" statement is equivalent to saying "In terms of primatology, the tree shrew is ancestral to the human." Despite our common lineage with prosimians, that's not a comment you'd make, is it?
I don't mean to be picky, but given how contentious this subject can be, shouldn't we be more careful in our phrasing?
Of course, one can never be too careful. But, don't get carried away. The multisegmented body plan (brine shrimp) is ancestral to the tri-segmented body plan (fruit fly). I don't insist on the exact phylogenetic ancestry of the shrimp to the fly, but, make no mistake, there is strong scientific support for the theory that crustaceans are ancestral to insects.