Restrict raising units to ones the player did not kill
If user has X raised units allow them access to an item that when equipped will automatically raise any units you kill
If user has X raised units, then allow the user to command those units in battle. For example, if user has 50 raised units then all of them will join each party battle. Maybe only some of them, depending on how overpowered that ends up being
Maybe some kind of mechanism that randomly brings monsters back from the dead when killed
Change raise dead message to something more like "$target reaches out from a grave and begins shambling about in the dungeon"