The issue is not so much the grass, but the quantity of gravel and sediment that has accumulated at all the seams, which is why the grass is now growing. Those areas became unused because there are quite a few spots with big enough pavement issues to preclude mod cars from going through, and they are probably even worse now after several drought years.
My opinion is that MW is on the way out as a popular autox site, and its still plenty big for anything you'd like to run there. Attendance at MW events is light at best, and the tire shredding seems to have worsened. I don't think there is much motivation to invest significant time/labor into the site, particularly if the other tenants out there are lobbying to stop renting it to us anyway.
If you do organize such an event, I'll come help.