There are several ways this topic could be viewed. In one sense, you're taking a car that was uncompetitive and putting it in a class where it has a shot. Even using 20 lb rims, it certainly has a better opportunity than in the previous class.

How many cars are being impacted? Opening up the rules to 7" rims has a much better impact on the drivers in the class.

Possibly adding extra weight to cars for using 7" rims might be an option. It will get complicated though.

Maybe cars being moved can have a dual classification for X number of years.