The current engine still works very well IMHO. I'd like to see it pushed as far and as long as possible. It would be great if it could be updated to use more cpu cores and add rain. I personally don't care for night racing. I used it once in ACC because it was there but that's it. When I said at some point they would have to bite the bullet and update I was actually thinking a new engine. I wouldn't mind if it was in the form of Raceroom 2, much like AC and ACC. I say a new game Raceroom 2 because I fear not liking a new engine and I'd hate to loose the current one if I did. I'm not completely sold on ACC's unreal graphics. Most of my hours in ACC was trying to get rid of the softness and get it to look good. In many ways Raceroom still looks better and feels better which is why it still gets more of my time. ACC is still a plan B for me. Used when Raceroom is down or it's late and multiplayer servers are near empty which happens around 7:30 at night here on the east coast of Canada unfortunately.
Hydroplaning, sometimes catastrophic ! In many places the effect is even dangerous as there is too much standing water when the weather is really bad Here's an example :
Completely agree with the current engine. It's a bit long in the tooth, but the natural clarity of the end result here is still one of the most convincing for me. I also like whatever iRacing uses. - I'm not a fan of their service, but they also excel in the 'natural clarity' of everything, but with the additional clout of DX11. PC2/AMS2 has an artificial (albeit pretty) look to me, and while ACC can look great, there's a massive performance cost to get there. I also echo your point on 'fearing a new engine', and losing/harming what we have. A related example here was the Time of Day stuff. It's quite pretty in a natural/subtle way and was a job well done on this aging engine, but it has a performance cost, and bar the odd occaison when I remember to change it for hot-lapping, mine just stays on 'noon'. I like the idea of night, but that must be all but impossible here atm. - I couldn't care less about weather. The continued investment in physics/FFB, AI, and sound improvements along with new content are all bang on the money for me atm.
Full day-night cycle and "visual rain" conditions (graphical rain effect plus reduced grip but not real wet tyre physics) already existed in GTR2 nearly 15 years ago. It's clearly not "impossible" just because they use DX9. But the effort required to do it properly with full wet tyre physics and dynamic lighting at night likely outweighs the benefits, since most online races run at noon in perfect track conditions even on sims where rain and night is implemented.
I remember from GTR2 track editing that you could put in a "rain line" (ideal wet racing line) so it was not simply reduced grip only.
I turn the lights off at night and my wife is spraying water from the windex bottle. As real as you can get
Well the wet tyre effect is already in the game, just leave the track then return and put your foot down, perfect depiction of trying to drive through a Tsunami. 95% plus will use wet/night once if at all, yeah sure a few hardcore endurance fans may partake in a weekly event but for the majority of users this ability is a waste of time and money as the best racing for a driver is on a dry sunlit track, now as esports progress this may well become important as things move toward a spectator sport, as fans like to see the introduction of jeopardy, as this fuels excitement. The only drivers who would wish for rain is the ones in the slower cars, as under wet conditions all things become more equal. In short, if I'm driving, dry and sunny, if I'm watching Thermo-Nuclear War, plus Tsunami. Go watch the chubby cheeked face of sim racing Jardier, he races ACC mostly at the moment and nearly always in the dry/day, yes the odd wet one and the odd dark one but mostly in the dry/day, so lets say 1 out of 10 races is wet (I'm sure it's less) no bean counter on this planet is gonna recommend to S3 that going through this long laborious task is a worthwhile financial decision. So in conclusion, you will get your rain and spooky nights but only once RR moves to a new engine or RR2 is announced.