My exact thought. It would be a relatively simple matter for someone with the right tools and machining/fab equipment to make something that was very compact and folded up into a small, thin package that could be easily stowed but then quickly deployed to make a quick sandwich at a rest stop.
Personally I would stow mine strapped to my Morryde MOLLE overhead rack that swings down. (Which, if I’m not mistaken, I believe you had a hand in developing, right?). That way I could stop, swing down the rack, pull out the table, unfold it and rest it on the tailgate, slide out the fridge and “voila” I have my lunch break station.
It sounds like those shortcomings are related to your desire to move around while having the table installed, and for that use case, a permanently installed table is probably the way to go (as it looks like you eventually did). My use case is different - I want something that is so easy to set up and take off, that it will used only when needed and then folded away when not needed. Therefore the two most critical design elements are (1) Must fold completely flat and very compact (less than 3/4" thick, ideally) and (2) must set up in less than a minute.
The approach I have in my head is a metal table surface (maybe with a MOLLE grid pattern) with bent-down edge for rigidity (or a sheet of HDPE), & a pair of detachable "arms" that stow inside the area made by the bent down table edges. Figuring out how to attach the arms and provide the necessary level of stability & support is the tricky part.