The detour will take you from Asheville North to Johnson City and then southwest to Knoxville.
Searches for some of the neat restaurants in Waynesville NC for food close to Asheville, then Johnson CIty TN...and Ridgewood BBQ just north of the Johnson City metro.
You will miss Canton, Newport and White Pine.
It will take a lot longer.
Taking a picnic and enjoying the overlooks along I-26 in NC would be my choice if I were wanting to absorb the wonders of a fall day in the mountains.