I think you are ahead of even most namenerds when it comes to feminine names for boys! I can see [name_f]Grace[/name_f], [name_f]Ada[/name_f] and [name_u]Simone[/name_u] on a little boy (possibly because of the names [name_u]Grayson[/name_u], [name_u]Asa[/name_u] and [name_m]Simon[/name_m]). I personally love [name_u]Avery[/name_u] and [name_u]Casey[/name_u] for boys but they are definitely unisex (though in my own social circle they lean girl).
[name_u]Raven[/name_u] would make an strong boy’s name with cool imagery. [name_u]Robin[/name_u] is nice too.
I posted a thread exploring the same subject, you might find some great ideas here!