If the tragedy of the commons results in people having to wear oxygen masks when outside, then so be it. Though community domes with their own oxygen limitations that are small enough to have a sense of unity would be a better option. Perhaps the opposition being ineffective and corrupt even though a better opposing policy could exist is intentional, this would sadly mirror reality.
Practically speaking, the scenario is unrealistic, as there’s no reason humans would be required over livestock, or why a fusion of animal and plant could even produce oxygen in a sunless world. The author has created this scenario for the purpose of it being a morally unsolvable problem.
If people have to buy their own oxygen, then poor people die on the streets. Where does that oxygen for those masks come from? How much money does it take to buy those lives? How many people can pay that?
If the government requires a heavy tax to fund public oxygen, then you get the horrors of Austercity. Compensated + voluntary transfloration gives people some agency in this disaster, but the vulnerable are forced into it by the Austercity gangs who seize the money. Their lives are short and miserable, but the citizens think the victims are living it up so they riot.
The problem isn't big state vs. big pharma, but that survival in this world depends on oxygen which is really fucking expensive in lives and money.
The best solution is honestly more research into cheaper transfloration. Maybe that comes from animals like you're talking about. The thing is, we've already been told that they can build enough nuclear reactors to get oxygen from water (Ch 20). But this system works for just enough people that positive change is being stopped.
Everyone is complicit in thinking the world just has to be this way.