Since all of the interior furniture in a Westsail 32 is plywood, there is no reason you can't cut out the existing plywood, and build anything you want. Make some drawings, and take careful measurements to make sure what you design will fit.
Also try to use some of the existing furniture as a starting point. Such as cutting a shelf back to within about 2" of the hullside, and laying the new plywood on top of it and screwing them together. A lot easier than bonding the new plywood to the hull.
I have lots of pictures of different layouts owners have done on their boats. Let me know if you want some. btaplin@westsail.com