...... If you're serious, this is quite possibly the single dumbest thing I have ever read. However, if your joking and what you actually mean that 40k is a fictional universe in which you can do pretty much anything you want, regardless of real world science or rules established by other fictional universes, then sure.
I indeed joked about the UNSC/Spartan thing(well, it is complicated. I will explain exact meaning later). But possibility about existence of female pseudo
-Astartes(I consistently said Pseudo-Astartes, NOT the full-fledged, 'normal' Astartes)? I am deadly serious, really. I don't think it is possible creating actual
female Astartes, of course. Because it is canonically, irrevocably, utterly impossible, I always well know that fact. But in the 40k verse, reinforcing, augmenting and altering normal human through genetically, surgically and mechanically is definitely possible. All of pseudo-Astartes is 30k era is augmented precisely these ways by Mecanicum, without exception. As I already said, it seems pseudo-Astartes making process is fundamentally different from that of normal Astartes, and they could never become 'genuine' Astartes. Let's see. If Emperor delivered Angron's gladiator army, then his 'sisters' would have been become pseudo-Astartes, no doubt. That it is. And one of the Mecanicum minor factions, Organicists, is a group of Tech-priests who esteemed biological enhancement as being equal in value with the cybernetics, a somewhat radical if not heretical position among the adherents of the Cult Mechanicus. That is another reason(although kidding is the majoris
in area of Spartan, certainly), I cited both Spartan and Mecanicum as an feasible example-if they really want, they could devise similar means augmenting normal human to become pseudo-Astartes. That is actually quite mundane conduct they are doing on their own not-so-weak flesh, and at least partly because of that practices they are categorized as 'radical', after all.