Hey guys, before addressing both scenarios raised here, important to note that ALL DecoNetwork sites communicate securely when necessary over the secure-decoration.com domain. This is usually when submitting a form (login) or during the entire checkout process. Our system has always dynamically switched domains when needed.
Entire site SSL is something we've recently enabled however it's currently limited to custom domains added directly to the site. When looking at SSL for global domains we begin to run into complications and limitations. We hear you on this and hope to add some functionality for this down the line.
In the meantime you can enable SSL by adding your desired domain as a custom domain into each affiliate store. I would recommend leaving the system domain set to use one of the deco-* ones. Here's a quick video showing how to switch your affiliate store domain to not be global one allowing you to enable SSL.