To expand on Mystic's answer, you can store data in a hidden save slot (script commands can access up to 33 save slots regardless of the number visible on the save/load menu) by using the importglobals and exportglobals commands.
However, it would be nice if you can read and write text files especially with scripts. There are lots of uses, from log files (you can use the trace command though) to character dumps and high score lists to adding some kind of level editor to a game, while being friendlier to edit by hand or copy between computers than a save file (and not having to overwrite some other save file).
Importing/exporting some other file types could surely be useful too. Probably mainly graphics: for the likes of
Stampo!,
OHR Pal (or maybe OHR Paint or Toy Town).
And no, it wouldn't be difficult to implement this sort of thing, except maybe for how graphics would be imported (overwrite existing?), but adding a set of file operations is a big step, and I have to wonder what the interface would be. A function to return the
nth line of a text file? One to open the file browser and search for graphics files?