The town green is an awesome plan. European cities preserve their historic down town areas by diverting through traffic.
Phase IV: Divert Hwy 9 traffic around the back (east) of the municipal complex by using Frazier/Forest & Hill Streets. Widen these streets to carry the heavy through traffic, and narrow Hwy 9 to slow down and discourage through flow. This would also encourage easy access to a second parking area in the municipal complex: For after hours and weekend events - when the city staff are not using the parking areas. Pedestrians would be more inclined to cross the old Hwy 9 if it were safer and in a more park-like setting.
Phase V: for bigger festivals build a parking deck in the same area designated for municipal parking now.
Commercial values and investment would naturally increase around Alpharetta, Norcross & Frazier Streets. Duncan