So the forums have pretty much been infested with the same pick-your-faction Civil War threads that won't change anytime soon. So I think this time we should look into the Civil War from a completely different perspective.

For those of you who have done the Ansilvund quest, we meet a distraught Redguard women who's husband was an Imperial solider(likely from the Hammerfell Legion under Decianus) who was killed at the battle of Red Ring. Now this crazy witch practically went insane over this and spent the last 25 years trying to bring her husband back. In her Journal she states that she seeks to destroy the Empire for the death of her husband and likely also the abandonment of her homeland. At the same time she also despises the Stormcloaks and seeks to destroy them too which according to her journal is because the Nords never came to Hammerfell's aid during their war of resistance against the Dominion since Skyrim was a part of the Empire at the time and only now when some Nords grow to resent the Empire, the "sleeping bear" finally awakes. Nords also don't know suffering at the hands of the Empire according to her.

So as we see in the dungeon, she and her fellow necromancers have been raising Draugrs and successfully bringing them under complete control to the point where the Draugrs have become machines for labor in her last attempt at bringing her husband back using the body of Holgeir a Nord warlord.

Before you fight her she tells you that she will destroy both the Empire and Stormcloaks and she plans on accomplishing this by by raising an Undead army against them. If you were not there to stop her, I imagine it would be quite devastating for both factions to face an army of Draugrs. To see all your ancestors and some of the greatest Nord warriors rise from their graves under the control of Warlocks against you would be quite a nightmare. Her dialogue gives good indication that after both factions fall she would likely use them against the Dominion as well.

What do you guys think about this and could she have possibly succeeded had we not stopped her? Even if her army were to be defeated, what kind of devastation would that bring to Skyrim and nearby areas?

Well, in my opinion, the only effective Zombie Apocalypse in a fantasy setting is the one with a disgruntled magic user at the helm.
She probably would have been pretty successful. If she started small, and turned her victims into soldiers.

She would have to raise nothing but Draugr Death Overlords to succeed.

She has plenty of Death Lords under her control already. One of them alone is probably enough to wipe out a whole platoon gameplay wise without a sweat. Lore-wise being masters of the thuum, a Death Lords could probably take on whole divisions.

Draugr wights hell maybe even Restless Draugrs are enough to easily make mince-meat out of both Imperial or Stormcloak soldiers, can't say about the Thalmor though. You only need a Draugr Scourge to start sending your enemies flying to Sovngarde.

She'd do plenty of damage that's for sure. The Empire and Stormcloaks would have to burn their dead and maybe even their Hall of the Dead to prevent her from running rampant. Since draugr don't really need to eat, sleep or drink they could easily run the armies ragged and finish them off in a few fell swoops, especially if they started within cities and worked their way out.

They'd have to fight brothers, sister, parents and ancestors...that'd be emotionally painful. Imagine the Companions having to face Ysgrammor and the 500, Ulfric may be forced to fight his father, etc.

It'd certainly be interesting.