I agree! When I saw the Jedi and their belt-over-cloak look I was already a bit disappointed, and the short sleeve cut of the Sith cloaks is really quite frustrating. ^^ Personally I don't care about practicality or seeing my armbands/gloves/etc - I would love long sleeves.
I do like the biomechanical style of Sith gear but at the same time I'd have loved to have a simple black kimono-type robe like most of you are saying. Then again when you see the trouble games generally have with animating cloaks ... As soon as it's long and billowy it starts cutting through the character or getting stuck or bugging. That's probably why we can't have overly long hair or long dreadlocks, or even trailing sleeves; perhaps it's a b*tch to animate? I don't know.
As for what I' d like to see - WHERE'S ALL THE FUR?
http://gameofthrones.wikia.com/wiki/Robb_Stark
I like to see my pure-blood Marauder as an aristocratic bastard with just enough compassion to appear not to care if his choices aid others (he's Light-side). So, having a British accent and being pure-blood, I'd love to see a bit of fur around the shoulders. Also, since we do travel a lot, fur adds that extra "traveller/pilgrim" look. It might look a little Medieval but, well, the Jedi robe does look like traditional Japanese clothing so hell.
Now I know that doesn't really fit with the whole "murderer" look but still, as someone said above, there's all the cut scenes and diplomatic things and meetings to think of.
Otherwise:
http://www.fanpop.com/spots/severus-snape/images/6237055/title/severus-snape-photo
Sorry to be Pottery on you all, but, either Snape looks like a Sith or the Sith have something on Snape. Billowy sleeves and a Tudor-ish button-up style.. perfect!
All in all, add sci-fi mechanics to a more medieval look and I'll be satisfied. And, more billowy elements please.