This is (literally) none of my business, but would you consider a cut down or basic open source version (hardware and software, with open software running in the proper hardware). Yes it'll be cloned by factories, and yes it will cut into sales no matter what proponents claim. (And yes it's probably more work than I imagine it is).
But also yes, it'll be genuine open hardware and might out live your interest in the project.
If you want a Free work-alike, why don't /you/ put in the work and make it happen?
I figure that the factory is exactly the adversary in the whole threat model? So why give them the keys to the castle so they can moonlight their own genuine batch?
You probably aren't going to do this whole rigmarole for small runs of devices like in the OP.
Serious question: why?
A local-only device with no telemetry can probably skip some of those