I've thought of that before. Normally you can beat up prefects and throw explosives at teachers and just run away, so why the hell not be able to just run away from detention? Maybe when you run away you'll just get a bit of a wanted level for a while before everyone's horribly short-term memory kicks in and forgets that you didn't do it. Another idea I had is if you could just beat up Crabblesnitch right in his office, that'd be pretty interesting too.
I'll try and work on this and seeing what I can do about it, I'll get back to ya if I get anything.