40 weeks out is a show stopper. I'm old and running out of time for new projects. If I was younger I'd likely start building with aluminum.
You can get aluminum sheeting. It's just a weird shiny version of plywood. You mig it or tig it together at the edges instead of gluing it. I used to have a buzz box stick welder. And torches. I sold it all off because welding and sawdust freaked me out.
Now I have a separate space with slab floor I could use for welding. I need 8 days a week.