Which units would you like to replace/add?

The zombies need to be replaced... They are the most ridiculous-looking unit.

It will simply create an imbalance; the Necropolis faction will be very strong, but the zombies have the function of protecting the skeleton archers.
With Death Knights, they have an ability that halves the number of units.
That's why they were removed from the Necropolis, but they were there initially because there was an upgrade for the knights.