My necro-to-be has a solid god complex, and would prefer to work more with constructs than true undead because of it. However, animating that which has been killed suits his purposes well enough. His version of the "great work" involves creating life more than restoring it. His aims also involve immortality through transference of consciousness into a more suitable, studier constructed form less likely to decay than his own short-lived flesh. It is his belief that the body, mind, and spirit are all separate entities, and that body and spirit are the sources of weakness. If only the mind exists, the gods cannot destroy the spirit and mortals cannot destroy the flesh. Immortality is thus achieved.

Defense for this theory exists in the presence of the mind both in death and in 3rd tier undead. The dead have spirit and mind, but destroyed body. The undead which retain their general conscious minds have their bodies, but are soulless. Because the mind can exist without the spirit, or without the body, he theorizes it must be its own entity.

Your necro can also use the Y'shai as reference: http://www.elanthipedia.com/wiki/Y%27shai

-pete