My own idea would be to add a lane in each direction to I-481 and rename it I-81. I-81 would be renamed I-81 Business (with the green-and-white shields), and then the viaduct would be taken down and replaced with a wide boulevard. (There already is a street along each side of the viaduct.) The remainder of the old I-81 freeway would remain as is, ensuring speedy access to such places as Destiny USA.
Sounds right to me. The “community grid” is just a glorified on/off ramp. 481 will become the real road.