So I guess what you're really saying is "this is awesome!", right?
I would be pretty disappointed if BA were turned after all the bullshit they've been through, all the while holding to their morals and defending the Imperium as best they could. The Sanguinor even showed up and bitch-slapped Dante when he succumbed to the Thirst and took it out on civilians once. That 10k+ years of resistance through constant hardship is a large part of what makes them appealing to me.
Of course that is awesome!
No, really, what i meant was that (perhaps in an old fashioned fluff perspective) in a truly grimdark setting, those who fight with such martial pride, bloody frenzy and even falling into a berserkerish state... even if they fight for the emperor, they feed Khorne. Even if they atone, pray, resist...khorne is there, feeding on the slightest fault. And fault is there in abundance (all those chaps in black armour and the X painted on it
So, i guess kabanda would want to keep it's buffet going on...
even if Guilliman reinforces/replaces the BA with an all primareis force, i recall it was said that genetic flaws kept showing, so... bigger BA, bigger feast for khorne!
Wouldn't that be awesome??!?