tl;dr for the most part, but anyway, for lfs to simulate racing as close as possible, engine tweaking / tuning should definitely be a part of it.
NOS would be an ok idea, but as im sure its been said at least once in this thread, most people asking for it are probably just asking for a hyperspace button
illepall, in which case they should be messing mekanik for the time being.
also, certain cars, down the line in production of lfs, should probably have more configurable bodies, akin to the wing angles of some of the cars in s2, but also the undercarriage of say nascars (flamebait i know).