Here are pics of a bed platform I made for our previous van that was easy to put in or take out and stored compactly in the garage. It was easy to make and easy to handle by one person. I wanted the bottom of the platform to be as smooth as possible so there was maximum clearance for bins, etc. This might help w ideas.
Bed platform is 3/4" thick three pieces 24"+12"+12"(could alternatively have been two 24" pcs) which is pretty much what is needed to easily get the platform in and out of the van through the back doors. Each of the three pieces had a 1"x1"x1/8" piece of steel angle on the long edge to provide spanning support. (Better would have been aluminum C channel, too). Each of the three pieces had three dowels On one edge made from lag bolts w the heads cut off after being screwed into the edge (predrilled). These aligned with holes in the adjacent panel to tie it all together.
The legs are 3/4" ply and butted up to the wheel wells to get 49" of clearance side to side. The clear height under the platform was 18". This along w 4" of foam brought the the top of the bed up to the window bay level for maximum width which was about 6 ft. Insulating covers were installed to keep the cold of the windows away from head and feet.
The legs were 48" front to back and 18" tall. Hinges attached thd leg to the 24" wide platform. Attached to the upper edge of the leg was a 1.5"x1.5" piece of wood to provide a stop for the leg when upright. This piece of wood also provided a way of securing the leg up right by using two screws through the platform panel into that piece of wood. This locked the legs in place. The remaining two platforms screwed into that piece as well which then made all the pieces act as one unit.
To store in the garage, the hinged legs folded flat against the bottom of the 24" panel and was stored on end along with the other two 12" wide pieces.
It would take me about ten minutes to put the bed in or take it out. It ran full width to the plastic panels.