Perhaps they will include special necromancy like perks under the conjuration tree. And I would love to have permanent summons! Perhaps with a blood (health) sacrifice? Or another npc life for example in the case of necromancy.

To me necromancy is the ability to manipulate life force. Where healers can 'grow' or strengthen lifeforce where it already exists, a necromancer has the ability to move and change existing life force how ever they choose. That could mean transferring life force from one body to another or storing it in inanimate objects like gemstones. Animating the dead then is really no more than taking life force from something else and moving it into a corpse. It gains 'life' again for a short time. Its not so much summoning something from another plane, like summoning daedra, but more like simply restoring a semblence of lifeforce in a corpse. Liches are simply those mages who have learned to stop the loss of lifeforce from their bodies. Vampires, for instance, need to steal lifeforce to continue their immortality.

The Mage Guild frowns upon Necromancy more so because it always results in obtaining/"stealing" life forces from others. Since its probably difficult to find 'willing' subjects to give it away.