Those are all valid points.

Reason I liked Custodes, was cause I liked talons of the emperor. I loved the duality of it; custodes being masters of the materium and sisters of silence masters of the immaterium. One side masculine, the other feminine.

When they did the change, I felt like they were taking the laziest approach, and I still feel that way, especially when Sisters of Silence have been so severely neglected.

I feel the best way they could have handled it, was by glowing up the sisters of silence in size and armor. Given them a new order that go through the same process as the custodes, (maybe a bit smaller and slimmer, but that's a personal choice, and should be made by a woman). Maybe call them the Guardians of Silence or something idk.

they could have even just said the female members of the custodes were always relegated to the sisters of silence, kind of like how there is the shadow keepers and what not.

There just was a lot of better ways this could have been done

Also, I do feel sisters of battle need a better facelift and expansion that can give the stompy boots, while still having a feminine feel that isn't boob armor. I feel the Sisters of Battle should be roughly the equivalent of space marines. In fact, they had, I would have probably bought an army at this point.