@Ryzza
The only thing with dirt bikes is they're not very good on the road what with skinny dirt tyres, so perhaps you should be able to swap tyres to some road ones like so.
http://i82.photobucket.com/albums/j261/Couch744/th_Photo-0022.jpg
And yes, that ones mine. Technically it's a supermoto when it's like that, as you generally have smaller wheels with tyres like that (compared to dirt ones) and mine also has bigger, better brakes thanks to Brembo. Though mine doesn't have the largest engine, there's plenty of supermotos with big motors, as big as superbikes. It wouldn't be hard to add a dirt set up to a supermoto or vice versa as the aesthetics only change around the wheel and it would realistically have softer suspension as well but I don't think many would notice.
Back to the damage side of things and on topic, there are plenty of panels which could come off a bike but you would then need to take more time modelling all the frame work and motor inside (this is of course more true of superbikes as dirt bikes have relatively exposed frames). Though saying that the same can be said for bonnets coming off on cars so it seems fair game to have body panels come off.
Perhaps a thread is due for dirt bikes/quads seeing as it seems to be a more popular topic lately, unless of course there is one.