OK, so this is my idea for a debug mode; Click to detach. You activate the app, and whatever part you click on detaches. Could be cool to see how a model works, or even to make films. (I got the idea from here: http://youtu.be/N1RKpdFjE4I?t=3m1s)
Already exists in the ui apps, have a looks, there is a set of three buttons, break all hinges, break-groups and deflate tires, play around with them.
But those detach all of the parts. My idea is when you turn this App on, whatever part on the car you click falls off, so say I turn it on, then click a wheel, the wheel and only that wheel comes off ect.
Bear in mind that the n/b is just a single object as far as the physics is concerned; it has no concept of parts. I'm no programmer, but I'm quite sure that telling a certain breakgroup to break is more complex than telling all of them to break, let alone telling a specific one to break on an event like a well-placed click. Could a dev weigh in here?
It is possible to break individual parts off. There is a thing called breakGroups. For example, the trunk hinge or hood hinge are breakGroups. Making an app for it could be done but it would require some of the game code to be modified.
I think this would come in handy inspecting collision damage. Remove the hood and front bumper to see the damage to the radiator support or whatnot.