Back in days of yore, when Only War was destined to be a source book for Dark Heresy, one of the things I expected to see was details of the more famous regiments of the Calixis sector (e.g. Brontian Longknives). We got the Maccabian Janisaries in the main book, and certainly now that it's about the IG in general they would take a back seat to the famous regiements from the entire Imperium.
But the Calixis sector is still highly relavent to the OW setting, is still is there plans to include the other regiments in later supplments such as Hammer of the Emperor? Is there a later supplement planned for Calixis regiments? Which would be a good place to add new regiments and flesh out a number of Calixis worlds, would that make it DH book or a cross over?
Here's a list of regiments I could find mentioned in other 40k rpg source books so far: