I guess it all depends upon his definition of "manageable." If I were doing that design I would want to be able to remove the HB & FB and then separate the platform/drawer frame in half down the length. on a queen, that would give you two pieces that are ~80" long x ~30" wide x whatever the depth is. The drawers would also be removable, so you should end up with four large, but manageable pieces.
Given the minimal nature of the side rails you should also think about a pedestal support or a series of adjustable legs to help carry the weight and prevent sag.
Pedestals are more difficult when you have a frame with legs because they have to be sized precisely so the legs still touch the floor, but allow the pedestal to carry its share of the weight. Carpet is somewhat forgiving of this, but solid floors can make it a bear to get right.
Legs could be designed to attach to the underside of the drawer frame at each divider. A leg can just be single square post with a
leveling screw on the bottom. If you want to get fancy you could design them to screw into the frame as well to make the easy to remove when it's time to tear the bed down to move. I'd set them back about 4-5" from the outer rail for a toe-kick space. I would also have them in the center where the two halves of the platform meet, for a total of 6 extra legs. That may sound like overkill, but if you'd seen what I have you wouldn't hesitate. Most mattress manufacturers require a frame with center support anway, otherwise it voids the warranty.
My 2¢
Charles