How do you even source tens of thousands of any of the multiple of crucial components these days? Fans, pumps, valves, whatever? You won't find them in your local hardware store, certainly not in quantities needed. Best bet is to find dozens of "kind of similar" pieces, which makes it impossible to test for quality or even streamlining the manufacturing process. Half of the world is locked down, so forget about shipping from China.
You end up with each batch being different than the last.
Dave, you said in your recent video that this is primarily a mechanical device, and that is absolutely true. Electronics in this thing can be rudimentary and easily designed (if we knew what had to be done), but mechanical part? That would take a well equipped machine shop to make a prototype and a serious manufacturing facility to start actual production.
But let's see what we can do.
Electronics design - check, we can do it.
This concludes our list of capabilities.
Let's see what we can't do.
Functional design (no one here knows what needs to be done. Ventilator designers and engineers have all long ago been poached by big players, rightly so)
Electronics manufacturing (World trade is grinding to a halt, do we etch thousands of PCBs ourselves in basements, each with their own method with blank boards we have in our drawers)
Manufacturing of mechanical parts (I have a lathe and a milling machine, possibly some of you guys too, but even if I could produce thousands of parts myself, I don't have nearly enough material laying around, and stores are closed due to the lockdown, furthermore I would never allow my piss-poor manufacturing to be the thread that someones life hangs on)
Enclosure manufacturing (you can't have the mechanism just flapping around. It's safety hazard due both because you can't sanitize it and because you risk someone snagging a wire and shutting down the device)
Logistics (if parts are produces in the basements of tens of us and we are spread around the globe, how do we assemble the ventilator?)
Distribution (once we have a product, do we just drive up an ICU and give them a box and expect them to use it)
Time (even with proper funding and human resources, this is a project that would take weeks just to get the right design, more weeks to set up production. Big players have been working on it for months, our efforts are way too little, way too late)
I've seen comments along the lines, "if the decision is between DIY and death, anything is better then death". I would say that is wrong. If health services are supplied with a huge number of substandard devices, and they count on them to be used once the shit hits the fan, they will be inclined not to seek proper devices, and when these start to fail left and right, suddenly there is a problem.
Let's leave this to people who know what they are doing.