Shale has been done.I don't think it will make much difference myself..I see what your saying about making it deeper and telling the riders to deal with it of do one ,but I guess Buster is giving them what they ask for(might be wrong).
I agree entertainment has to be high up on the list,but having a happy camp of riders is needed as well.
Keep it as it is(the dirt) and make the track shorter and a lot wider might even it up between the riders( bit slower racing,so not needing max horsepower) or as you say,chuck more dirt on and let them get on with it.