For a mid-season fun run, or in-between seasons, have a "random combo night" where 7:30 on the night of the race Wally randomly selects a car and track from the AC content and we all go in "blind" and have to learn the track and car in an hour, qual and race. It would reduce the impact of some people having the opportunity of practicing for hours vs others with a lot of activities which means they can't prac before hand.
Another idea is a fixed setup season in something like the MX 5 cup car. I think again this would help those that haven't got time/knowledge to be tinkering with setups for hours vs just some good old fashion flat out racing. All you'd have to do is get a fairly stable setup that everyone could drive and you are done for the season.
Oh, and we talked about this previously but I'd still love to do an endurance race with driver swaps.