I'm looking at running a warband of World Eaters that have fallen away from their Legion's dedication to Khorne. Still a rough and bloodthirsty band, but one that believes a bit more in tactics and somewhat less in berserk charges. I have read that the World Eaters were originally called the War Hounds before the Emperor found Angron. I guess what I'm envisioning is a World Eaters faction that rejects the path taken by their Primarch (re: dedication to Khorne - they're still fully Chaos Space Marines) and goes for the road of Chaos Undivided. In pursuit of this, they have reclaimed their original Legion name. I know that the World Eaters are heavily fractured into innumerable independent warbands, but how well would this angle fit in with canon?

1. Near as I know, the legions were simply numbered before the Emperor found their respective Primarchs.

2. Lots of Khornites are already into strategy, though their strategies inevitably focus on melee combat, the World Eaters do have commanders and champions who are more than mere berserkers. This is actually an aspect of Khorne, some Bloodthirsters are insane berserkers, some are martial champions with an honour code they stick to, and some are cunning and savage commanders.

I found the War Hounds reference on Lexicanum from one of the Horus Heresy novels. There appear to be several Legions that were renamed after being joined with their Primarchs and new homeworlds, and the World Eaters are among them.

The Canon of the Horus Heresy novels is that the Chaos Cult infiltrated into legions trough the warrior logias that most of the Legions had (with "little" help from the Word Bearers Chaplains).

So, its possible that there were logias whose allegiance was not so strong to Khorne, as they were based upon free thinking of their members. Also, because of the "accident" that earnt Khârn the surname of "The Betrayer", your CSM could have realised that adoring only one God would have fatal consequences for them and split from the Legion. They may even think that the Word Bearers used them as berserker puppets introducing the Khornate cult and that the Legion spirit had been betrayed, so they return to its former name.

This resource might help. It's a fan made summary of what is known about the pre-heresy Space Marine Legions, largely for the purposes of those who want pre-heresy TT marine armies.

It includes data on the War Hounds (colour scheme etc) sourced from the Horus Heresy novels. It's a narrow and focussed website, and is all the better for it. The "visual archive" project is particularly good - it repeats a lot of stuff from the Horus Heresy books, but some of the the fan made art is genuinely brilliant, particulalry Aerion the faithful's portraits of each primarch.