imho opinion, LFS needs a big, heavy 4 door car, like a Chevy Caprice/Impala (the round shaped one like the american police use)
Big heavy engine, RWD that seems to always wheelspin (on telly
) would be quite tricky to master racing and very fun for autoX and generaly playing about.
It also needs a 24h / prototype car, (as many have already said) something that has all the characteristics of the GTR cars from LFS and F1 roots.
Lastly, a supercar. Their are sports cars, road cars, formula cars and GT cars, no super cars. NASCAR wouldn't go amiss either