(this belongs in chaos board)
What do you mean? Any chaos army can take seige warriors(or whatever the skill is called).But if you want to include things like no limit on oblitorators or servo arms or looted veichles you'll have to play an iron warriors army. But you don't have to play with the silver/gold/chevrons color scheme. If you want to use any scheme you want and you make it clear to your foe you are using the Iron Warrior rules then it is okay.
