That may be the least coherent plan I've ever heard. If I offered you a leaf blower taped to a sack, that would absolutely make the situation worse. If you need a ventilator you're not in a position to make decisions because
you need a ventilator. Come on, this is a fantasy and I think you know that.
If you're lying there, gasping for air, that's not the time for the nurse to wander by and ask if you liked the Dyson BlowMaster 8000 or the Siemens 300A Servo Ventilator, and to explain to you the pros and cons.
What you need is a proper, certified ventilator you can get by ramping production of existing ventilators, not starting over with some bits of sticky tape and string. You can force companies, in an emergency to produce them [1]. That's the only sane plan in an actual emergency.
Let's briefly break down the "treat like a child" bit. A child is someone who's not capable of making decisions. Neither is someone who needs a ventilator.
> Safety testing is less important when treating dying patients who have no other options.
Safety testing is more important because sometimes applying a useless device will do more harm than doing literally nothing. Something is not always better than nothing. How else can we, to your point, weigh the risks of having it vs not having it if we don't evaluate them?
[1] https://en.wikipedia.org/wiki/Defense_Production_Act_of_1950