IDEA: Customizeable command system
Make a command-prompt-like interface, except one that the user could customize. Like adding external files (similar to .bat files) that the user could add to a folder, then be able to run from the prompt. This would require a lot pf thought and programming, but i think it could be fun.
(It may also have real-world applications, like sending the program out to employees and keeping the command folder on the network computer... though this would have to provide some way for the user (or admin) to specify where the user-specified commands are located...