A couple years ago, my favourite housecoat was past it's day. I carefully laid it on some ugly fabric I had, and traced all the pattern pieces around with a magic marker, then cut the pattern from the fabric. Then laid them onto the polar fleece yardage I was using. It's oh so cuddly and warm! And the bonus is, you can make it as long as you want!
If you wanted a quilted housecoate ... you could quilt your yardage and then cut the quilted fabric. Or cut out the pieces and quilt them before assembly.
Depending on the weight and warmth desired your sandwich could be ... terry and cotton? fleece and cotton? double cotton and batting? flannelette and cotton? double flannelette? Possibilities are endless!
Here's another pattern ...
http://www.connectingthreads.com/patterns/Kimono_Robe_Pattern_Download__D991495.html