Today when I was playing around with the game files, I accidentally deleted the default system, which made the game literally unplayable* so I had to reinstall which, thankfully, didn't delete my rockets and sandboxes.
Still, it is problematic.
What I propose is basically for the default system to automatically restore itself if the game does not detect a solar system to prevent the game from becoming unplayable. Take the mobile rocket game 'Spaceflight Simulator' for example. In that game, you can freely add and edit new planets/moons (And they're all in seperate files, too!) and if you delete the Resources folder which has all of your planets and stuff in it, it will restore itself back to normal the next time you launch the game. This would make for an easy way to restore things the way they were if things go south.
*By literally unplayable I mean once I pressed the big play button that shows up when you load up the game, it would do the normal animation except Droo is replaced by a water planet and the Main Menu has no buttons or anything.
@SupremeDorian Yes, we do plan to split the planets out into separate files eventually.