Constellation Changes

How hard would it be to modify the Constellation to double the width of its body? It would then allow for greater cargo capacity, crew quarters, perhaps a second deck to make it absolutely a ship to own. Another issue I have about the Constellation class is having engines on the ground itself. With a wider body frame, pylons can be included to house landing gears and a ramp to allow vehicles to drive into the cargo area to minimize cargo exposure on the ground.