I'm thinking something with the stand-up collar and button top like this:
But with long sleeves and front opening like this:
I'm also liking the princess cut of that Vogue pattern.
Obviously, since this is for a robe, it will be much longer. I am thinking past the knee at least. I also want some comfy pants for underneath. Those will be very easy and I'll be using a pajama pattern. The hardest part of this project will be finding the perfect fabric....