A mage-oriented "cursed form" is a fine idea, but a lich isn't it. For one, it's too mage-centric... a mage and thief can be a werewolf, and a mage and warrior can be a vampire, without impeding much on their play styles. But how would a thief or warrior play as a lich? Not to mention that lichdom itself doesn't grant power. The power comes from all the extra time you suddenly have for study and practice.
I really don't see a reason why lichdom wouldn't give you a cool ability or two, but whatever.
Still, in Tribunal, the lich king does fight you with a sword, so it seems that a lich can something other than a mage.
Even if it couldn't that wouldn't be too big of a problem.
There's also that werewolves and vampires are essentially temporary forms. You become a werewolf when you want, then change back after a short amount of time, and you become detectable as a vampire only by not feeding for three days, then change back by feeding. A lich is a lich, always and forever. Rotting flesh, no muscle, all of it. "An illusion spell" is such a cop-out, particularly since it's never occurred before even among the most powerful liches of Tamriel's history (probably couldn't get rid of the smell). Plus a simple Dispel would reveal you.
There is no more dispel in TES.
And what's wrong with the illusion spell?
Then there's the matter of a cure. Not even the best mages have been able to fully resurrect someone to their pre-death state. Vampires work because the body is still intact, it just needs to get your biological functions going again after removing the Daedric taint. Going "divine intervention" would also be a cop-out, especially if you made yourself a lich on purpose in the first place.
Mind explaining what's wrong with having a deity returning you to your normal form?
And even if there isn't a cure, so what?
Actually, I would prefer it that way myself.
Finally an action you do would have an actual consequence.
I don't think a Vampire Lord would work either. A Vampire Lord would be a more powerful Vampire, and it doesn't make sense that a Vampire Lord would be so different gameplay-wise from a regular Vampire.
Unfortunately I can't think of any known creature that would make sense for a mortal to be cursed to become, which could still allow you to function in society for the most part, and would grant boosts to mage abilities while not working against non-mage characters. Maybe some kind of were-atronach, but that seems a bit silly.
I still think that a lich is a perfect one.
So what it doesn't allow you to be warrior or a thief?
Some things are simply not for some characters.
And I don't see why help from one of the Divines isn't a cure good enough, but like I said, even if it doesn't have a cure, it's fine.
Only thing I find a bit of a problem atm is how will hide the fact that you are a lich.
For now, I say an illusion/alteration spell will do the trick!