There's a two sided suggestion here and this is one of the two ways I would like to see it implemented. In my use of XPM I'm going to have a product and several additional paid dependent add-ons (i.e., expanding the add-on itself) and since it requires a license to the add-on, I was going to use optional extra(s). Yes, I understand that they are usually used for things such as Branding Removal, but bear with me. The additional file download is what I was looking for, but it doesn't allow me to independently version them and restrict them to versions prior to license expiry. So, I would like to see that. Or conditional products (my other suggestion).