That leaves us with Codex CSM which while good and perfectly balanced at the time of it's release, failed to meet the above criteria IMO. It just wasn't Chaotic, especially compared to earlier editions. Chaos should be insane as it's title suggest. Because of that failure, the future of Chaos weighs heavily on the release of Codex Chaos Legions. As such I did some brainstorming and came up with a list of things that I think really will ensure the success of the release in both terms of game mechanics and fluff.
4- All 9 legions represented via unique list/rules/characters- I think all 9 legions should be in this codex, which ties back into number 2. Basically it would work like Codex SM. If you don't do anything silly, you would have the black legion, plain and simple, like in Codex SM you would have the Ultramarines if you did nothing extra. Then to make the other legions, you start doing things (marks) and taking certain units (cult troopers) and characters. Characters will more than likely alter the rules of the army more so to reinforce the feel of your chosen legion.
5- Daemon Prince able to represent each legion- These guys were elevated to daemonhood from Marines of their respective legion. They need more than generic Daemon prince rules to show this. And you have alot of cool crazy potential here, and alot of cool crazy potential with GW/FW models.
6- Some insanity to the book. The last codex, while balanced, wasn't Chaotic- As I said earlier, CSM wasn't "crazy". I really want alot of choices and variations in the army, plus rediculous units. This doesn't mean Random though. Chaos dreads are a perfect example of a crazy unit gone wrong through randomness, as the random rule really gives them no added benefit. This leads me to point 7.
7- A reason to take dreadnoughts. As it stands there is very little reason to do so. The random matrix needs to go, and there needs to be ways to make them characteristic of each legion just like the Daemon prince. And sweet models already exist from FW, so there is no excuse (it's not like GW hasn't done this in the past, Colossus and Hydra in codex IG is a perfect example, or even the waveserpent in the past). Oh, and Contemptor variants would be a good addition, seeing as we are talking about armies that have been around since the Heresy.
8- If a character exists in Codex CSM, but needs to be in Legions, MAKE SURE HE IS IN LEGIONS. You know who I am talking about. Kharn. The Betrayer. The coolest single character in Warhammer 40k. A battleaxe wielding maniac. Sure abbadon should be in this too, but Kharn NEEDS TO BE. Fabius not so much, why? He is a renegade now, not an Emperor's Children brother anymore. But Lucius the Eternal is, so he should be.
I think 8 points is perfect for Chaos, so I am going to end there. I really can't wait to see what comes out, and while I know I won't get all, if any, of the above, this is really a positive direction forward as I see it and is my opinion of where GW should take their IP and franchise.