I may not have much say due to my not being at the event. I just would never run with weather change on, due to issues like this. In the event weather is on, and rain gets to the point where it would cause a Red Flag, if the race is before the halfway point, they would wait it out for hours before calling it quits, and then restart the following day. If the race is past the halfway point they would just end it.
I remember for this year's GT6 Daytona 500, I simulated the rain delay by just announcing a Red Flag and switching it to night time. However, in the case of randomized rain that could halt the race at any time unplanned, that's not something I would have in the race settings.
Although NASCAR has raced in the rain on rare occasion on road courses they do not on ovals because it banking + rain = too dangerous, so I can understand adding in rain as a factor. There have only been 4 times that NASCAR has raced in the rain (that I know of) The most notable example I can think of is Suzuka East qualifying in 1997. (Which was the only time I know of that the Cup series used rain tires.) The other 3 that I know of were Nationwide races, 2008 and 2009 Montreal and this year's Road America race. At Road America, there wasn't an aforementioned tire change either, but NASCAR did mandate one, unexpectedly.
In summery, I disagree with racing in the rain (at least for a NASCAR league), however, the actual Nationwide Series has before and it seems like trobes handled it like NASCAR would've. (Although I disagree with forcing a Caution and mandating the driver change to rain tires and think that drivers should just change tires when they need to, it is what NASCAR would've done.) Racing in the rain is a possibility, but seeing how it's something we can control with GT6 settings and rain just causes issues, I think it is best avoided.
I'm not really sure what was going on in Peagle's case here, but NASCAR wouldn't take away a win, just points. Also, trobes, you really need to publish the full rulebook. If you need to rip from mine, that's okay. For the drivers, penalties will get issued from time to time, it is not a reason to freak out, you simply appeal it civilly and move on. I think somewhere in the GTP OLR it actually mentions appealing penalties in private. (or maybe that's calling out other drivers on things.) EDIT: After checking the OLR, it seems like initial penalties and appeals should be conducted privately and resolved before being reflected on the official log.