Oh dear, oh dear. You just don't get it!!!!
The licenced cars are encrypted. For everyone. Tweak can't get round that unless the encryption is removed (it won't be), thus with or without permission Tweak won't be able to edit the non-demo cars.
I won't have a model importer for LFS, but there is a CMX model importer for 3D Studio. There won't be an exporter (from 3DS)/importer (to LFS) any time soon, although it's technically possible to make your own if you wanted. However, seeing your Lambo in LFS wouldn't be an improvement - I'd hazard a guess it'd be utterly shite, because you don't appear to have a clue what you're talking about - the intricacies of suspension setup, engine/drivetrain positions are probably way too complicated for you - stick to Minesweeper.