I'd love to see an option that allows selection of only classic skins when you choose "Random skin on play."
In my quick search I found a thread that mentions the Skin Randomizer plugin, but there's still faults with it. (Namely it's only on startup and it's geared for WA 2.xx.)
If I use the UI checkbox, I still get random skins. I still like modern skins so uninstalling modern skin support isn't a solution.