Bill Tindall, E.Tn.
Beds stay in place for a long time, so flat-packing for a move is unimportant.
The first bed I ever built when we were first married and had no furniture was made from half lapped 2 x 4's and 4 x 4 pallet skid legs, much as you describe. It did in fact get moved from MN to Buffalo and Buffalo to TN on the top of the car. But when I built for more than function.....
....I expect this bed to be moved. To accommodate moving it is assembled with bed bolts.
A footboard serves no structural functionI think you would agree that it does for many styles of bed and all traditional styles.