Thanks to Phil for forwarding me information on the officially sponsored ride from Atlanta to the ABW and PWPB in Chattanooga. They appear to not have one specific organized ride but are providing assistance to individuals or small groups who plan their own. Given the many variables this is a great approach. It also obviates some of the pesky legal issues.
With that in mind the plans for an organized ride to Chattanooga will be abandoned. No one has shown interest anyhow. I will put together a list of suggested routes and, lodging and stand ready to assist people from the airport since I know of no good way out of BNA on a bike. Heck, I feel lucky to get out of there in my car.