James Horton's Profile

If your still going to have the 80's air con duct, I think you should embrace the 80's, ditch the curved wall and put in roller shutters from a shop front. You could get them tagged and sprayed or even a vinyl graphic treatment in an urban street style, if that's your thing.

http://www.flickr.com/photos/gandara/2872387959/in/set-72157607354627756/

It would inject a bit of more colour to the room and becoming a talking point, whilst providing a flexible space.
Roller shutters come with doors, so you can have part or full width access.

If metal shop shutters are too much metal for you, you could try curtains, a wooden blind or even a paper wall... as they would allow some light through and allow for making shadow puppets in the bedroom.

http://www.designmuseum.org/__entry/61355?style=design_image_popup

http://www.in-kamiyama.jp/_wordpress/wp-content/uploads/2008/04/00000342.jpg

If all else fails, knock it down and divide with, large bits of furniture, then who ever buys next can do what they want.

good luck.