The proposed system uses exactly such a thing. But a mask doesn't work because you want to put pressure into the lungs, not inflate the cheeks. Masks only work temporarily to assist a patient that is still breathing relatively well on his own.

And there is nothing technically preventing the use of those bags right now. But you'd have to have one person standing beside each bed, 24 hours a day. Which means a hell of a lot of foot traffic, and those will get infected with a high probability. They also need to be trained to a minimal standard.

It's not practical.

Masks do and can increase pressure in lungs, the reason intubation is used is to provide fluid drainage, prevent choking. So that the critical patient does not drown. Other than that, they're equivalent. Cheeks can puff out only so far.

I have never used masks that way and I would worry about the fit. But it may be possible, temporarily, especially when you hold it down.

Procedurally most physicians seem to reach for the intubator as soon as there is any trouble breathing, even though that takes longer than putting on a mask.

My understanding is that squeezing the bag would have a high risk of covid infection. The only way this solution would help the curve is if covid survivors were doing the squeeze.