Huntsville would be a good location. Lots of engineering talent including a significant Boeing presence, a large airport with an inter-modal cargo terminal with rail access and close to the Tennessee River for potential outsized barge cargo.
The old Kelly Field in San Antonio would also be excellent. Boeing already has a facility on the old Air Logistics Center.
Charleston, which already manufactures the 787 fuselage and has a 787 final assembly line, is also an ideal choice.
Do they still have the runways at Brooks? Should be some empty space there.