Well I'm a so glad to see we are back on topic! :)
@ProfFuzzyWhiskers:I actually have come across many who wanted her to have that bounty hunter tag.
The whole reason I started this thread was because of obvious contradictions I noticed by cg's reasoning. The separatists tag comment is a great point.
@ProfFuzzyWhiskers: "As such, amusingly, if they gave Asajj the Sith tag, they would actually have to remove the Nightsister tag, as she was never both at once. And nobody wants that."
I answer your question with another, when was R2-D2 part of the galactic republic and the rebellion at the same time? And where Kanan and Ezra ever really jedi (personally I like them having the tag). But if they can can be considered jedi, then Asajj should be considered sith.
My main reasoning is she is a darkside wielder, was a sith apprentice, and wields traditional sith red lightsabers. I'm not saying shes a sith lord, the marauder, and the assassin are sith but not sith lords. And I feel if you have those abilities and get strength from the darkside, you should benefit from darkside synergy. Also keep in mind this is purely in the name of fandom, she would not be truly viable with the sith because she loses major speed by leaving the nightsisters.
With all this being said, I remain skeptical that they will ever create a sith "snapshot" version of Asajj. It is clear that cg is focused on the separatists faction specifically right now. So maybe just maybe there will be a new separatist/ sith Asajj. But for all those who argue she was never a sith, I say you are flat out wrong