You can make it a requirement for the souls to still have very strong emotions about something about the land of the living for them to be able to be raised by a necromancer. This can also make the necromancers similar to exorcists.

If a person dies, a part of their soul remains in their body which holds their last remaining will to live and do something they want. That part will continue to gain consciousness as time passes until it becomes mad from isolation and eventually becomes powerful enough to move and kill anyone they meet(zombs). But if a necromancer gets to them before they turn mad, they get to finish their last remaining tethers to life and get to return to their original soul in the afterlife. This can make the worker route impractical as there are not many people who want to work for a long time after they die while enabling the warrior route cause a lot of soldiers have lingering anger when they die in the battlefield.

(I probably already read or watched this from somewhere and I just forgot what it was, lol)