Stuff that can be saved on your hard drive that if you know what you are doing, can be edited directly.
Settings
Costumes & Power Customization
Mission Architect files
Demo files
Popmenus and other mods
Logs
Popmenus and such get loaded when the client starts, and if there are errors, they'll be pointed out in the client log which is different than the other logs.
Logs if enabled just get added to, and not recommended to edit while running.
Costumes, Power Customization, and Mission Architect files can be loaded at any time, but they do go thru sanity checks.
I would imagine if there was a base save & load, it would be a fairly complex file, but certainly doable. (Item plus location, facing, tint, etc...)
Loading would probably be doable, it would strip stored items, and make sure stuff was legal and sane. (No buffer overflows, etc...)
There's a bunch of other stuff that would have to go into it
Loading and Saving just a room. What happens to stored stuff on loading? Hard fail, or "Are you sure?", or can we still store what's here in what you're loading?
I can see this being used to tweak a base where you want to reorg, or setting up a completely new base. It's a large range of options that would need a lot of planning on development.