Individual saves within a single sandbox

Alternate title 1.7 years later for clarity: Save slots inside sandboxes

Currently, as far as gamesaving goes you can only quicksave and make different sandboxes.

What would be nice is if you could make individual saves within one sandbox so that if you quicksave yourself into infinite doom, you can load a different save instead of either being stuck in an infinite loop of explosions or doing undo flight and potentially restarting the whole mission if you did it all in one game session.