To repost what I said on FB, of what what they listed, WW2 female Partizans for sure.
Female Afghan and female Boxers are both good ideas if historically accurate. Something Napoleonic since silver bayonet exists might be good (with guns this time😆).
Bulldogs is probably the Death Fields set that might benefit the most from a female counterpart set that does not have one currently (skirts instead of pants), I think the rest already have headswaps.
Given how vague the Dark Age era seems to be with costumes, armor and clothing, WA should just do a general "women of the dark ages" box with parts and a body to do one armored shield maiden per sprue or box instead of "Dark Age Irish women" since it will cover better for the decline and fall range too that way.
Of whats not listed the clear obvious choices right now are:
Dahomey amazons for History and Death Fields (good excuse to do FFL for history and they have a movie coming out so the folks that live in the Americian media bubble will know about them).
Female Knights for fantasy (why in the name of sanity would you do Vikings, Saxons, and Norman women that are debated on weather they are even real warriors or not and mostly don't have sagaboards when Fantasy Female Knights have been an asked for thing since 28mm plastic sets where invented practically).
Female barbarians cause they are good for classic fantasy, VSF and pulp.
Female Adventures for fantasy, (same deal as female knights).
"Warrior Women of Warring States China" (since WA is doing Warring States China🥰).
Maybe Soviet Female Soldiers for WW2 and the early coldwar.
If they really want to do VSF I suppose female Pulp/Victorian Adventurers would be a good set (though one might be able to cover those with fantasy Female Adventurers for VSF and the WW2 Partisians for Pulp).