Let me think. That's the mod I've heard of, with my opionion\questions:
1) The Necromancer
I never played it but I was said it is good. Though Giskard and this community have a troubled past, so I don't know how much The Necromancer is compatible with the major overhauls - In fact I would like to ask to anyone how I can use that mod with Fcom, for example.
2) Oblivion Necromancy 1.6 or Modular Oblivion enhanced (lichcraft plugin)
If you wish to become a lich, these are the two choices you should look for.
I've tried both, and basically I find the latter better than the first.Becoming a lich is a subject that always fascinated me.
In the end, for both mod it comes to taste: Oblivion necromancy is more complete because you can make your own pets, summon an undead unicorn, and some other stuff that makes basically a cute mod.
There is a slight problem though. The modder never added a "disguise" spell, so you are basically stuck in a lich form that practically scares everyone in the city. I didn't have time to check if even dark brotherhood guys get scared but I feel like the obvious answer would be a no.
If I was able to, I would have added the spell myself and went for this mod.
Modular lichcraft is basically a great mod. It gives you the best of the "lich" part: you can basically choose between three types of liches, with different perks and weaknesses. I found it cute, though I hate the fact that I'm forced to wear some stuff that are basically "autoadded" after you have morphed into a lich.
So in the end it is up to you.
3) Another cute mod I've heard of is Moriarcis - City of the Dead .
I've never played it, but I've heard all kind of bugs, but the only one that I remember vividly (even if I read about it years and years ago) mentioned that if you use it with a mod that adds spell ( Midas Magic - spells of Aurum ) there is a slight chance that your mana gets tweaked to the amount of 9999. Hearing of it made me uncertain If I wished to test and mess my Oblivion.
Good luck