Yeah, so I wanted to try the haircut thing on my vampire so I created a save right before I started the vampire cure quest. After I got my vampirism cured I got a haircut and had the serana chick turn me back into a vampire. After that I kind of liked my old haircut better so I reloaded my save and my hair\appearance had changed to the new haircut. It had done this with all my saves for that character. So if you want to make changes to your vampire create a save next to the haircut chick and have serana change you into a vampire after it will effect all of your other saves for that character. This only worked for vampires tho I tryed it on a non vampire.

Edit: never mind the new haircut goes away when you turn the game off.

This probably works for other things besides haircuts.

Is this really a solution to the problem, though? Or is it just a tedious, tedious, workaround to a problem that never should have been present to begin with?

Very nice. http://images.uesp.net/c/c4/Fishystick.jpg for you! Welcome to the forums!

Question: If you get cured, then get diseased again, do you keep all the perks from the first time you had vampirism, or do you have to re-earn them?

you keep them