a cool feature i'd like to see for an OS would be a "secure delete" option in the right click menu that will delete the file, write over it with garbage data, then delete the garbage data.
linux already has a "move to trash" and "delete" option that simply deletes the file without moving it to trash, so the option to have a bit of file shredding could be nice.
i honestly don't know how that kind of stuff works 100% but you can get the idea i'm going for.