I thought about the 'layers' coming off when we were discussing this very issue in the F1 forum.
But what I thought was that the sidepod that does come off could be shaped to fit the other bit that's left on. Presumeably the sidepod is a different bit of the car that can be seperated in the 3D moddleing bit, yes? Well, have the bit that joins up to the car on the sidepod fitting with the crumpled part of the car that's left. It would mean only a small bit fell off, and wouldn't be as noticable.
Or, could something not be done with the damage model editore Dumass made so that allthough ti fals off, it doesn't actually fall off, it just disappears. There is a bug with a lot of the cars that mean when say, the front wing or front wheel(s) come off, the entire nose of the car up to the cokpit is graphically duplicated (not physically) and comes off too. This could be reversed couldn't it (as this bug is now being mended) so that although things physically come off, they don't graphically?
And yes, I do appreciate the impossibility of modding GP4!
I also think that the last GP game should be made incredibly editable, or, they should give the code away (they'll never need it again, will they) to some editors of the series they know well of(ie Rene Smit and the GpxPatch team) so that the game can be edited and live on forever!!!