Apparently Night Liches can only dominate weaker undead, and I'm not sure if dominated undead lose control over undead that they dominated.The more annoying thing is that if it's similar to vampiric spawn domination or an evil cleric's control undead ability, there is a cap on how many HD / levels' worth of undead you can control and any excess go free. Since each Night Lich presumably has a different HD/level equivalent, calculating the exact combination could be tricky. Also, it presents a major risk, what if someone disrupts the control somehow (in D&D a basic Protection From (Alignment) will do)? You'll have your trusted lieutenants running wild.
It works if you can inspire genuine loyalty, but that takes time and the approach usually has to be tailored to the individual.