Well that already looks like bending over something that wasn’t meant to be used like that. I can see SGO as a great system for checkpoint style save system. Even for storing single persistent world, but our case is bit more complicated.
User will be able to download maps from external server. Manually at the beginning, later with some in game routine. It would be impossible to modify SGO based on new file being downloaded. It will be much better to have a blueprint node that is able to return list of maps out of list of files present on file system.
Also we want some sort of metadata with each saved map like name, description and other stuff that can be displayed before trying to load the map.