enigma1 - 11:22 am on Sep 30, 2010 (gmt 0)

Using multiple SKUs for the same product may cause problems. Consider using a base product and then use attributes to cover options for a product and generate the sku.

In any case your product page should function the same when a product is added to the cart or when a product is added to the wishlist. In other words treat the wishlist as a secondary cart. A secondary storage similar to the cart storage should do.

I am not sure how you involved the categories tables with the products and wishlists. I don't think you need it.