The Horus Heresy is a collection of legends for most of the Imperium, sure - but that doesn't mean that a chapter with all that pre-Lorgar heraldry will just be waved through by, say, Inquisitors of the Ordo Hereticus, fellow space marine chapters or even Guilliman himself. 40k is a setting filled with paranoia and distrust, and so these guys would immediately find themselves at gunpoint of a dozen different factions. Plus, it is kinda unoriginal. Taking a bit of inspiration from the traitor legions is a great idea, hinting at the possibility of stemming from traitor geneseed is fine too (ADB had an interesting interview about the matter a while back).
Maybe it'd be a good call to read up on the homebrewing guides here on the Liber subforum and go from there. That said, it's still your chapter, your army and your idea - you can always just follow through with it, even if it's disagreeable.
Edited by AHorriblePerson, 29 August 2020 - 01:42 AM.