Additional Form of Grouping in Catalogs?

Currently in C1 Pro, you can stack images in the catalog, but only if they are variants. I understand that this can't be repurposed to multiple related images (like multiple shots in a sequence, or alternative exposure shots, etc) because variants don't have their own file, but I'd really like a way to associate and stack multiple image files together in a catalog in C1.

So for example you can select any group of images, choose to group them and they get stacked, with just a pick image showing in the browser, and you can expand/collapse them like variants. Thanks!