I play on Xbox, so I would have no idea if this is even possible, but I had an epiphany for a mod which would automatically add 4 spells to every NPC's, and the player's, Spellbook. They would be Lesser Powers, and completely free. The 4 Spells would be this:
1. Transfer Consciousness (Combat), transfers consciousness and the NPC or player that your consciousness just left would go into combat mode.
2. Transfer Consciousness (Magic), same as above but they would use magic spells in combat as opposed to regular combat.
3. Transfer Consciousness (Stealth), same as above but they would stay in sneak mode and not attack unless undetected and they had a ranged weapon.
4. Transfer Consciousness (NO Movement), same as above but they wouldn't move, or attack or do anything.

The 'Transfer Consciousness' effect would let you 'become' the target NPC, as in you control their body exactly as you controlled your last body. Quest NPCs are unaffected, and you go into all the regular factions as well. So, you could use it to control a Necromancer, then attack all the Necromancers and quickly use it again to change back into the player.

My question is, is it possible? I have no plans to make this mod, as I'm on Xbox, but I would like to know if it is ever possible in case I get the game on PC.

For the computer http://wryemusings.com/Wrye%20Morph.html is what your looking for.

For XBox - no modding talk allowed here - I'd expect this thread to be locked at any moment. That is unless you are asking for mods only for the computer.

I don't think he was after an Xbox mod, I think he was just wondering.

Wrye Morph isn't quite what he was after I'm guessing, but it's similar. I probably wouldn't be too hard either to use Wrye Morph's engine to produce a 'consciousness transfer'; just morph the player into the target and create a duplicate of the PC as an NPC with a suitable AI package.

And then what consciousness (AI) would posses the normal player character?

Wrye Morph is buggy enough and even Wrye warned of this.

Create a copy of the player (I don't know if createactorfullcopy would work here) and store them in a holding cell. When the player casts one of the spells teleport them in and give them a suitable AI package.