I can understand wanting to tweak the cars. I'm one of those guys who likes to tweak everything too. But in reality, I think what sets LFS back a little is that there are far too many adjustments. Some of the adjustments are unreal to the point of spinning your car if you change them a little.
Adding adjustments or tweaks to the engine/tranny, etc could only make the situation worse. Now, the question here is what do we want to spend our time doing, racing or engineering a car? So far what I have seen is that I spend far too much time with adjustments for the time I spend racing.
Let's be real. My racing team spends about one month tweaking the adjustments for one monthly race (and more than one guy testing the cars). How do you like that? I don't

For that reason, we have a team "engineer" who scopes out the sets and the rest of us test the cars and report our findings to him. This is important on long endurance races where more than one driver gets a chance behind the same wheel.
But there should be a starting base that should not be modified to preserve equality among the racers. So far the developers have done well in restricting some features and that makes all of us equal when it comes to the track.
Don't get me wrong, there are many things I'd like to see changed in LFS, but it is by far the most exciting and realistic simulator when it comes to online multiplayer racing.
Buying and S2 license would be a good investment if you asked me.
Best regards,
Jim