You have actually hit on something that is being found by physicians working on this problem. A physician in Italy, I believe, one of the hardest hit countries, has written a published paper that putting covid patients on ventilators may well be what is killing many of them. The ventilators are designed for lungs that are stiff and hard and push a lot of air into them. Covid patients have perfectly fine lungs, soft and flexible, but filled with a virus, and the ventilators aren't designed for that. What these doctors are finding, and I have seen some in New York interviewed now as well, is to try as hard as possible to keep the patient breathing on their own as much as possible, and giving them oxygen in less intrusive ways than a ventilator and turning the ventilators down if they do go on them. Now, this is practitioner data, not double blinded scientific studies. but these doctors are reporting lower death rates by doing it this way. The death rate on a ventilator is around 80%. They are reporting much better than that by keeping as many folks off of them as possible. So your methods might not work, I have no idea,. but your idea appears to be right.
What you might be missing is that by the time someone is on a ventilator, their lungs are full of fluid, and there would be no way to replace one liquid with another (saturated with oxygen or not). As it is, it is apparently very difficult to aspirate fluids out of the lungs enough for the oxygen from the ventilator to make its way in.
The doctors have experience with ventilators so I'm sure they will figure out the best approach if you end up needing one. Since you don't have experience with ventilators, it is unrealistic to think you can figure out a unique solution to deal with Covid.