I like the idea of the army. A large unit of Cultists to perhaps infiltrate and put pressure on objectives / soft targets, and push back roadblocks.
And a heavy wave of mechanised / daemonic close combat vehicle & mob killing big guys. Very scary
One thing I don't think synchronizes well is the Chaos Lord. If you give him a jump pack, Blade of the Hydra and a Bolt Pistol he's a lot faster and a lot more lethal
(with the 1 commandpoint Bolt of Chaos (1d3 mortal wounds), the bolt pistol is kinda awesome in a pinch). And incidently the same points.
Otherwise the Lord will not be able to keep up.
Other thing to think about is the Havoc squad. 4 Missile Launchers on 8 bodies is a lot of points for not too much dakka.
Perhaps you could exchange them for 3 (Slaanesh) Obliterators?
The point difference isn't that big, but Obliterators are harder hitting then 4 Missile Launchers (if you have the models of course).
I took down an Imperial Knight with one round of shooting of those Obliterators. So they can be amazing (with a bit of luck, and my opponent forgetting to rotate shields).
Marks?
Also, what Marks are all those Alpha Legion units?
- The Daemon Prince could benefit from Tzeentch (extra Psychic power strategem).
- The Chaos Lord could benefit from a Mark of Khorne (2nd round of combat strategem if need be, expensive though)
- The Cultists could benefit from a Mark of Slaanesh (2nd round of 36 x 2 autogun shots, combined with Veterans of the long war, is pretty cool).
Anyways, great list even without modifications.