1. We have wind. Fog/Rain come together. Snow not that important, but would be about the same time as rain I guess. Humidity isn't that much of an issue for the cars. Air temp is already modelled, but static. Making it variable won't be that hard. Wind temp - you mean wind chill? Don't think that matters in a simulation - at least not for about 30 years. Night driving would come with the environmental upgrade (rain, light cycles etc). Track temp already modelled (iirc) but static.
2. Not all parts need to be simulated. Parts can be fudged I think. Trying to simulate a whole car, including CFD and FEA in real time on complex constructions isn't feasible. At best the cars will be broken into areas where sub-simulations are sort of carried out on a very very simplified basis, which is what West Racing were suggesting (don't beleive they were really modelled the whole car in every detail - it's just not possible).
3. Damage model will come, but isn't that important. Try not to crash. If the damage system was less forgiving that would be sufficient, without teenagers testing the damage model by wrecking and limping around on track.
4. Racing line effects grip - more important imo than rain or night.
5. If you have to turn on the ignition, fuel pump etc, put on seatbelts (do you want another player or two have to help you?) then you'll turn off a lot of players, including purists (like me). It doesn't improve the simulation at all, it just wastes time. I can see that some parts are more acceptable that others - starting the engine via a button (NOT the mouse) might be okay. Warming up an engine might be nice, as would out-laps and parade laps, but for leagues only. Silly ones like belts or helmets etc just to use keyboard keys is pointless (imo).
6. I don't want to reach for a mouse whilst driving. nKP is very very bad here (Kunos is crap at user interfaces). A wheel or keyboard button is okay.
7. Shattering glass doesn't excite me at all. Racing glass is designed to not puncture tyres.
I hope that a lot of these do get coded, and I agree it will be great. But some of the ideas must be toned down if we want a racing sim rather than a race-car preparation and adjusment simulation.