Posting in the Magento forums has been disabled pending the implementation of a new and improved forum solution which should better serve the community.
For new questions please post at magento.stackexchange.com, the community-run support site for the Magento community. We will be providing updates on the new forum solution soon. For questions or concerns please email firstname.lastname@example.org.
You can easily include hidden products in your URL for adding to the cart. If you built an extension and you know which products where always associated with the product, it would be easy to add all the products to the cart in the background.
In a sense I am adding multiple products to the cart through one call here
We have developed a module which extends standard magento’s attributes/options functionality and allows to setup flexible configurator based on rules which can be managed by admin. Also it allows your customers customize product colors/textures.