hmm i am not sure it would requoire alot of modeling. you would only need to close off the robe ends making them narrow right?
Also, if that is too much, you could always take the sleeves from a BB shirt which has close off ends and then apply them to a robe no? ( that might be easier)
But i cant model so I might just as well throw hot air into the sky or somethign :shrug:
The problem with grafting sleeves from a BB shirt on is that they won't line up with the robe body - there would be gaps, and they would look horrid. And making the robe ends narrow is more work than you think: since vertices were moved, the sleeves would have to be re-weighted, and that can be fiddly. Plus, you would have to do it for
every... single... robe. As modeling goes, it's not a hugely complicated job, but it is a fairly big one, and it would have to be done by someone who knew their way around Blender or Max.