Seems like way too much work. You can buy a perfectly good case for $100, less if you go used. I know there are more expensive cases out there, which must be super duper. But I don't know that you're easily building one like those.
I built one waaay back in high school wood shop. It took forever, I didn’t know what I was doing, and the case died with my old Hondo II bass that I learned to play with when it didn’t survive a fall off a truck. I would approach it differently today with the advent of much better materials available, but not going to as there are better cases available in the $100-$200 range than what I can do.
I built a badass hard case for my last custom build for around $60 and got all of the hardware at a local hardware store. Since it was so easy i think I’ll start doing them for all builds since cases have gone up in price and most are a mix of cardboard’s and other cheap materials.
My wife helped and we used plywood, memory foam, yoga foam block for neck rest, leather and some hot glue and staples. Just make a plywood box, cut it down the middle and attach the hardware and foam etc. Took about an hour total and saved easily $150+ for the case quality it ended up making.
You can buy a much more lightweight and plenty strong case that is made of a plastic-like material formed with strengthening ridges on the outside and has a formed foam-like covered liner that is plenty protective. Your ease of getting it around will make it easier to handle, and you will likely to get it out to play often. Your back will thank you for it, too. Mine is made by SKB.
You don't wanna know what's in the hotdog....
When my US tele showed up, the seller basically viewed the broken case as packaging materials.
I knew it would hold up if the hinges got reattached, as the aluminum trim parts were still intact. So I pried up the glued in Styrofoam with a fabric facing, used a screwdriver and pliers and fixed the case.
So yea, Styrofoam. And molded plastic.
I'm certain you could build a pretty solid case for under $200, but finding the right kind of dense padding foam would be tricky.
I'm staring at an unused sheet of 1/16" veneer type ply, and know I have 7ish glass cases incoming at work which will ship with multiple 30"×75" pieces of the right kind of foam that I could use. Plus I have guitars without cases.
And I'm not doing it.
I turned a backpack from Amazon into something I can use to haul my Frenzel head to gigs, and it reassured me that if a "case" doesn't reasonably exist for something, I can do it. But I'd need a reason.
When I build stuff out of wood, it has heaviness to it. When I'm playing with foam, I don't think to myself "this would protect a $1000 instrument ". So no.
I'm thinking short scale fender gig bag that holds 2 guitars. Maybe.
There's only 1 time that I contemplating building a case, and it was for an unusual acoustic guitar that was very odd shaped and didn't have a case, and no case would properly fit it. So.... I looked into all of it and suffice it to say, it would've cost me at least 300-400 bucks to make the case, using quality parts etc. I ended up not buying the guitar so it was moot. No, I wouldn't make my own case unless I had no other choice. Lots of work and lots of $ vs. the benefit IMO
I've thought about this too. Making it light enough while retaining the structural support to prevent damage to the guitar during accidents is a daunting task that could take quite a bit of experimentation to achieve.
The issue is that I don't like the options. The materials being used seem like a waste of resources for something that is meant to be highly functional, and secondary to the instrument. If it's a deluxe model, it's understandable why someone would want a nicer case.
Injection-molded plastic, tolex, styrofoam, freshly harvested wood, leather—why use any of these materials at all for a case? There must be better options for new cases out there.
I guess it boils down to where you go with your guitar. If you want to take it on a plane then a metal one would be necessary. And no matter what you decide you probably won't get away without using some of the resources you mentioned. The reason they use plastics is because of weight.