A quick note about Renegade Command Squads
Something I didn't mention about this unit in the Warlord post, because I'm an idiot who misses obvious things, is that unlike the Imperial Guard version you can add extra men to the Renegade Command Squad. The basic cost covers your Arch-Demagogue and four Disciples but you can add up to ten more Disciples. Renegades & Heretics are usually a bit more of horde than Guard so having a few extra meatshields around your Warlord is probably a good thing.
The Renegade Command Squad is the only actual unit in the HQ slots, the other options being individuals you buy in groups and split across the army.
Rogue Psyker Coven
One of the big problems I have with this list is that the basic psykers don't have access to Daemonology. In fact, they don't have access to Disciplines at all and instead generate a power from a D3 chart included in the army list. The powers aren't bad: there's a Strength 7 Blast, a Malediction and a Blessing but I really think a Chaos army should be able to have Daemonology without having to burn the Warlord on it.
On the other hand, they have two wounds and a natty little rule called The Daemon Unbound. The way this rule works is that when the Rogue Psyker takes a wound from Perils Of The Warp they become Possessed, gaining Weapon Skill and Strength 5, Rending and Feel No Pain (4+). Also on the plus side they're one of the few units in the army with stable Leadership: 8 for Psykers, 10 for Possessed.
They're by no means a bad choice and its fun to see them explode into monsters when something goes wrong but I would really, really have liked more ways to get Daemonology into the army.
Renegade Enforcers Cadre
Chaos Commissars, basically. Like the Psykers you buy them as a group but deploy them separately. Unlike the Psykers they can't be deployed independently (which would, admittedly, be pointless) and have to be assigned to a unit. They can only be assigned to Renegade Infantry Squads, Renegade Mutant Rabbles or Renegade Veterans, which is an oddly restrictive list.
Anyway, once attached they give the unit +1 Leadership (to the usual maximum of 10) once their Uncertain Worth has been determined. You also get a re-roll on failed Leadership tests after they pop a model of your choice from the unit. They can't be the Warlord but we've already established there's sod all point in having anyone other than the Arch-Demagogue be the Warlord.
Psykers or Enforcers?
Unlike their Guard equivalents both Psyker Covens and Enforcer Cadres do count as HQ choices on the Force Organisation Chart so you have to choose between them to remain Battle Forged (the Command Squad being compulsory).
I'm not quite sold on either as a superior choice but I think there are enough ways to compensate for Uncertain Worth that Psykers might be a better pick than Enforcers in most cases. I might not like how restricted their powers are but the D3 chart isn't terrible.