I see what you mean, Bob, and I'm all for realistic tweak usage too...
Using premade cars for online racing would be great and would practically add 'new' cars to LFS.
However, I also hope that you won't leave out the possibility for users to tweak/modify cars like in past tweak versions. Ok, this is mainly useful offline (although can be used in private organized races too while using identical presets), but the point is that there are hundreds of cars that people would want to recreate (or at least try). Not all just increase power and add awd - many take it seriously and get great enjoyment from LFS by just driving their correctly 'tweaked' rl cars with researched specs and accurate setup parameters...
The second aspect here is tuning - and I mean realistic tuning/upgrading of a car. Say I have a preset of rl car in tweak and want to try various modifying possibilities for that rl car in LFS: I want to see and feel what wider than stock tyres, less weight or bigger boost pressure in turbo would change in car's handling and performance. So by having great physics engine, LFS can be used as quite accurate car modifying simulator - if not to benefit your rl car projects, then just out of pure automotive curiosity and enthusiasm.
That said, there always will be whiners, crackers, demo'ers, noobs, kids and so on. But that isn't a reason to ditch something that is good when used properly...