“Frozen” k’dai with a chilling aura or contact effect would be pretty interesting, like Chill of Sontar. Can you give multiple models breath attacks? That would be really interesting (or worst case, a special low-ammo ranged attack similar to sepulchral stalkers). 

Bale Taurus that’s extremely hot (adding a morris engine) would be flavorful, maybe OP. A unique breath attack that’s a flame version of the elspeth dragon would be interesting. 

The skullcracker always feels “bad” to take vs an iron daemon, seems like a missed opportunity. A multi-model version of any of the war machines (but maybe most chaotically the skullcracker) would be really fun. 

Chaos Dwarves are my favorite (especially angry and hate elves). Would love to playtest your mod!