Ultimately the goal should be to use as much of the US 17 Bypass as possible. Freeway conversion that includes the use of frontage roads as one way pairs is an underused/undervalued design in NC. Oftentimes to the detriment of existing businesses that lose significant revenue when greenfield routes are selected.
IMO I-99 should pursued to provide a continuous route number following I-795, I-40, I-140, The Carolina Bays Parkway extension, and SC 31. I-795, I-140, and SC 31 would be decommissioned along this new interstate. The ultimate goal would be to extend this new interstate to Charleston. This new route would alleviate I-95 and further boost economic development along the coast in NC and SC.