I (1/24th of the league) agree with almost all that is said here, with one exception
I think it is important to do the weather in a way that nobody spends much time practicing in the wet (like this season). This is to make every single driver's preperation for a race as simple and little time consuming as possible.
Every driver have their own time budget to become competitive. Some need only an hour or two to reach their desired pace, others, like myself, need more time, 4-5 hours or more. If we create an environment where drivers start preparing for an eventual wet race, everybody will feel (rightly so) they have to do it to be competitive if it rains. This means that either you will have to spend more time preparing, or you will be less prepared for an eventual dry race.
Preperation time is a key aspect in running this league. The more time that is required, the more "stressed" the group will get. It means bigger spread in times, poorer race quality and a higher "leave-the-league" frequency. (my opinion only of course)
I think the wet races we had this season proved that we are all capable of doing a good race preformance in the wet even though not preparing spesifically for it. We might be a second or two slower than out potential, but that matters little when it is the same for all.
If I was to dictate how to tweak the weather for next season, I would only make one change, namely to increase the general likelyhood for rain in a race (or qualify).