Does anyone do this? Is it possible?

As a pure mage I have worn mages robes for 31 levels, nothing more. Yes it is possible. Yes there are enemies that would one hit me, draugr death overlords, spriggens were nasty, could not mess with frost trolls or the big cats.

Basically it forces you to
1. Not get hit
2. Use the environment to put space between you and enemies

Its not easy obviously, but it is 100% doable.

If your an assassin I recommend using light armor. I breezed through the game killing everyone before they even knew I was there. If they found out I was there all I did was turn invisible, that might sound overpowered but its really fun and Assassins aren't supposed to be detected anyway. If you focus on sneak, Archery,One-hand, and illusion your pretty much set. Just don't bring any companions because they mess up your stealthiness.

Depends entirely on your build. Low level assassins without cool illusion perks might find it quite tough at first. Also, if you're perking into Smithing at all, remember that your armour will eventually reach the same cap as heavy armour.

Yeah, just sneak. You can actually pull it off in clothes since on master, there is no difference between light armor and clothes.

I'm on my 4th longterm character and it's absolutely doable. Like someone else said, I've done nothing but robes too. It can get frustrating but it can be done. My Alteration got up to 100 pretty fast because you have to constantly remember to cast Xflesh spells. My conjuration when through the roof too. There's no way to get through any respectable enemies toe to toe in robes.

As for light armor, certainly. Especially when you get glass. I didn't like wearing it because of its appearance but it does the job well. I eventually stopped wearing it and went back to wearing the TG master armor instead. No self respecting thief/assassin is going to go sneaking around looking like he's wearing a really lame leftover costume from a St. Patrick's Day parade.

Just train a lot to get the LA skill up and take every relevant LA, sneak, backstab, and archery perk.

And just so you know, Heavy Armor ain't no picnic on Master either. My current character is all about the heavy armor and at level 28 he's still getting killed with one hits by Deathlords. It's been really disappointing. It's difficult to tell the difference in protection between light and heavy armor on Master level.

It depends on what build you like to play. If you're a fighter/barbarian type who wants to wear light armor then I would recommend taking the Lord Stone early on to give yourself some extra mitigation. In the long run, it doesn't make much difference what armor type you use because you can easily get maximum mitigation using either light or heavy armor.

I did it- pretty easy and it ends better than heavy. Pick up lord stone and invest in a trainer (riften shopkeeper) early in your career. keep everything in top smithed condition.