Zombies could fight with the weapons they had when they were alive, for example peasants would have crude weapons.
Though a unit can be made to run amok this will occur regardless of how close they are to their necromancer, so out of control zombies can be difficult to code.
Also how will this faction function. Since the Tomb Kings use soldiers made from the preserved dead they only have low levels of soldiers but since Vampire Counts use undead that are far more available they should have greater numbers. A possible handicap is to only allow this faction to start with weak undead units, with strong units available at the end of the tech tree (no middle level units). This would encourage early attrition until this faction has worked its way up the tech-tree.
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