Related Products Recommended by Category, Automatically - Automatic Cross Sell

Ok, It'd be awesome if I could randomly display 6 products on a product page from a related category.

I'd like for this to happen as automatically as possible so that I don't have to set related products per product, in the back-end.

For example if under the edit category "Pants" in the back-end had a related product category field we could specify that category "Belts" is related to all products in "Pants". This would then generate a related category box (randomly displaying 6 products from "Belts") on every individual product "Pant" page.

So if I was on a product page for a pair of pants I'd see 6 belts under it.

I was thinking if we could tweak the sql query in the new_product.php to pick up the appropriate related category this might be possible, relatively easily.

Ideally this would be integrated with the Cross Sell Add-on so that you could over-ride randomized 6 related products with custom select related products.