Something I have been looking at is how Chaos Space Marines can establish an effective, cost-efficient “fire base” that the rest of their army can maneuver around, especially given how CSM are lacking in firepower compared to Tau, Eldar, Necrons, their Grav-toting Loyalist rivals, etc., etc.
Here is what I have come up with so far:
-“Imperial Strongpoint” Fortification (consists of Bastion with Void Shield and Quad Gun, Aegis Defense Line with Ammo Dump)
-“Daemon Engine Pack” Formation (Warp Smith, Forgefiend, Maulerfiend)
-Chaos Space Marine CAD with 1 x Nurgle Obliterators, 2 x Relic Sicaran Predators with Lascannon Sponsons, and HQ/Troops “to taste” (i.e. maybe Nurgle Biker Lord and Plague Marines).
Not counting the HQ/Troops, all of this costs 226 MBs, which is quite a substantial chunk of your army, but provides the following:
1 – Warpsmith mans the Quad Gun on top of the bastion, giving you 4 x TLed BS5 Auto cannon shots a turn against Flyers and Skimmers, so very solid air defense. He also can reduce enemy cover and repair friendly/curse enemy vehicles, plus he is solid for counter attacking into close combat with 2+ save and 6 x S5 AP2 Power Axe attacks on the charge.
2 – Nurgle Obliterators join the Warpsmith on the Bastion, making for majority T5, plus 2+ save and 4++ cover from the Battlements (add in the Void Shield for even more protection). On top of the Bastion, they have excellent LOS and can shoot their various Lascannon, Plasma Cannon, Assault Cannon, etc. weapons all game long at range.
3 – Forgefiend deploys behind the Aegis Line (getting a 4++ cover save), but within 12″ of the Warpsmith and 2″ of the Ammo Dump, in turn making it BS5 and able to re-rolls 1s to Hit… this translates into 8 x S8 AP4 Pinning shots at 36″, all with 97% accuracy, so more than enough to kill most vehicles and also put a lot of wounds on enemy troops (this is the perfect weapon against Wulfen, since it denies them their armor save and their FNP, IDs their 2Ws, and kills them before they can get into close combat!)
4 – Relic Sicaran Predators also deploy behind the Aegis Line and within 2″ of the ammo dump (if possible) to benefit from the 4++ cover and also for re-rolls of 1s to Hit for their Lascannon Sponsons. They obviously provide a strong shooting base with their TLed Accelerator Cannon (S7 AP4 Heavy 6 Rending, Ignore Jink Saves) and their Lascannons against all targets and further compliment the Obliterators and Forge Fiend shooting.
5 – Finally, the Maulerfiend (which is a required “tax” from the Daemon Engine Pack formation) can either move aggressively toward the enemy, if required, or hang out behind the Bastion, out of enemy LOS, and wait to “counter-assault” enemy CC units that move up to engage the CSM gun line (it is pretty ideal for the counter-assault role, since it moves 12″ and can charge with Fleet, plus hits hard with S10 attacks at initiative and is fairly durable with AV12/12/10, IWND, and a 5++ save, especially now that grenades have been nerfed majorly in the Assault phase).
While this is a lot of investment into just the “fire base” for a CSM army, if you are playing at 1850-2500 point level games I think it can be quite competitive and you still have enough points to flesh out your army with good objective seizers, close combat troops, Psyker support, etc. to make for a genuinely competitive Chaos task force.