I've seen systems that are just a single tray - maybe 18" by 18" and maybe no more than a foot deep? They were uncovered so they had plenty of air circulation. If they were kept indoors and had a screen to keep out flying critters, it might suit your purposes. You might want to think about a lid, however, depending on your own environment and needs.

My only question is how quickly well-fed worms would outgrow something like that. My honest confession is that I've only recently used a system like that, so I'm no expert; I've only "seen" it done. I used a plastic tray that was 18" x 24" x 6" deep. I only used it to store finished VC and worms until it dried enough to be sifted. I fed the worms in there, kept it indoors, and it never developed a smell or attracted any bugs in over a month. The VC stayed remarkably (and annoyingly, considering my purposes) moist and the worms never tried to escape. Wood might have helped to regulate moisture better. However, that was starting with finished VC, not bedding and food.

Good luck to you, and make sure to post pics of whatever you and your mad carpentry skillz come up with.