I think such a road would only benefit people travelling to Huntsville from Hartselle south, and unless completed it would be a road to nowhere.
Now if you think REALLY big picture and build an entirely new road continuing connecting Huntsville with Columbus, MS. From where from where the road intersects I-65, the road could keep going to intersect US 278 near Addison, AL, duplex with US 278 to east of Double Springs, and then continue southwest to intersect with I-22 and AL 13 near Eldridge. From there, continue south, maybe south-southwest to Fayette, and then use AL 96 the rest of the way to Columbus. Maybe this entire extension could be AL 96, or maybe give it a north-south number since it is really more of a north-south than east-west route. I know this is fictional territory, but it would provide better regional connectivity in the western part of the state.