You may want to have a look at https://worldbicyclerelief.org/en/

May be participating there is more worth your time and creating a larger impact than starting a new project. Their bike is not as hardened at the one you have in mind. But it may be more practical - at least until the actual apocalypse.

Thanks, Florian. I'm going to let WBR know about my design. In the long run, I'd like see a bigger entity take an interest. At this point, I don't know how things will unfold, but it should be fun finding out. In any case, as it is out there under an open license, my apocalypse bicycle belongs to the world now!