i dont think it will be possible.
if you can export than you can import.
after we can start to make gt5 ourselves.
it would be good but again ..impossible i think
Drop the DVD to your harddrive and the start searching for patterns that could resemble geometry - Unless, of course, it's encrypted, then you'll have to decrypt it first, then look for patterns, then re-inject your changes onto the DVD image, keeping the checksums in place, encrypt it back with the correct keys, burn DVD, play ;-)