Ok, haven't completely given up on this outdoor thing yet. I know there are rules about what you can erect in places like yours but could you do a kitty veranda? I went looking for dmc123's threads from when she and her roomie got theirs last year. Maybe something like that would let Angus get some fresh air and save your furniture and whatever else he is using.
http://www.pets.ca/forum/showthread.php?t=51337
http://www.pets.ca/forum/showthread.php?t=52087