Instead of editing the Lua sandbox to change what each plugin can or can't access, could there be a permissions dialog per plugin, accessed from the File -> Plugins dialog? Everything that's set in the sandbox could be set with GUI objects, such as disabling the OS library (or parts of it), the IO library (or parts of it), DLL loading, LuaSocket usage (if that's ever added), and other concievable options.
The preferences would probably be stored in the global preferences mysqli database, or in its own database. It would probably also be global and not linked to any specific worlds, because if a plugin needs access but isn't given it, chances are it's probably not going to work as expected.
I also suggest changing the behavior of SaveNotepad so it won't save outside a certain directory (perhaps a 'notepads' directory under the plugins directory), but make this configurable in the Permissions dialog.
The preferences would probably be stored in the global preferences mysqli database, or in its own database. It would probably also be global and not linked to any specific worlds, because if a plugin needs access but isn't given it, chances are it's probably not going to work as expected.
I also suggest changing the behavior of SaveNotepad so it won't save outside a certain directory (perhaps a 'notepads' directory under the plugins directory), but make this configurable in the Permissions dialog.