I believe to build one today, with today's materials, would give a much more transportable board.
I use foam insulation board today for lots of things. It's sold in big sheets that're different thicknesses. The most useful is just under an inch thick. I made my wife a "quilter's ironing board" with the stuff a few years back. It's a "board" that lays over the standard ironing board. It's much wider and has a square planform. The insulation board wouldn't be strong enough by itself so I glued it to thin sheet plywood. That combination would be rigid enough for a wing board. It wouldn't be for the q-board, so I glued longerons and such to make the q-board work for her. She covered it with iron board stuff and it works great. The backed insulation board would work great for our size and shape wing board, and you could get her to pay for all the materials if you made her an ironing board with the wasteage.
Or tell her the basement needed some insulation over in the corner. Lean your wing board in that corner with the foam showing and.....
The hinging would still be a design challenge. If you wanted no gap and a pinnable upper surface that is.