Products that require ownership of another product to purchase

A way to make a product require you own a different product (on Jinxxy, I don't think its possible to do cross-platform) before you can purchase it, could allow for products reliant on base ownership to be more easily sold!

(In my case, I would be using it for my facetracking DLC's and make it so they have an alternate version without any patching required, that requires you to own the original base before purchasing)