I think that we might have to distinguish creating cars and creating  tracks. I agree that creating user cars in LFS might not be the best  idea, because it somehow destroys the "state-of-the-art balance of  power".
A different story might be the idea to create user  tracks: I can imagine that it might be possible to form interest groups  which are able to create very interesting content (I am sure that many  germans already thought about having the legend "Nordschleife" track in  LFS ...).
I would offer to spend some of my spare-time and help  with the know-how I can help with. Using laser scanner techniques as  used for the Rockingham track sounds like a very reasonable approach -  the problems begin probably when optimizing the model to fit to the  graphics engine and when modelling the different surfaces of the  track... 
I could imagine that there are some more people like me  willing to contribute without monetary interests, but this would  require an opened framework. Another way this could be done is by  contributing content through a review gate (or similar), so that the  devs have the possibility to judge the quality of new content and decide  about the integration or rejection of submitted new content (similar to  what's been going on in the linux kernel development).
But at the current state this is just a dream what could be 

 ...