Chaos Primaris Marine, a single prototype, a single warband?

[Zephaniah Adriyen]

Okay, so. I just got Shadowspear for Christmas. I already own a Vanguard Librarian because I eBay'd for one during my Blood Angels days and reused the model for my Raven Guard. I still have the new Libby on the sprue... I'm thinking Chaos Vanguard Sorcerer. I can't think of a single reason other than there aren't any yet in lore NOT to convert him up into one. I could even have him be made from stolen Primaris gene-stock and some warp ery. Thoughts?

[Filkarion]

I use pleanty of primaris bodies for chaos marines conversions, especially for champions/characters and they work very well, explaining things with "in the warp, glory makes you bigger"

After all the blackstone fortress lord is bigger by a lot that normal CSM