The government hires an independent contractor organization (I guess The Aerospace Corporation and NASA people and former-FAA people from the time the FAA had technical people, etc.) to do a blue ribbon commission style full analysis of the plane, at a huge cost in time and budget, and publishes the whole thing, scathing as it is to Boeing. Some people might get fired, in both Boeing and the FAA, but that doesn't matter.
The independent contractor organization gets carte blanche to declare any issues as "preventing certification", and to suggest any fixes, and oversee Boeing implement the fixes and the tests (what the FAA should have done). When they sign off that the plane is safe, the FAA signs off (as a formality, because we don't trust the FAA) and airlines based in the US start using the plane where jurisdiction allows (maybe only in US, maybe in friendly countries). After a while of no crashes, other jurisdictions will allow it and other airlines will buy/unground it.
Boeing pays the government for the work of the independent contractor organization, in equity I guess. The government holds the stock until the stock price rises after the fixed plane succeeds in the market, and then sells.
Note I know nothing about anything, so the above is fan fiction.
Great idea, but I think Feynman died awhile back.
They need to put pilots through simulator training of both kinds of MCAS failure: (1) MCAS goes nuts and needs to be turned off, and (2) MCAS is not there to save you when you need it.
So long as Boeing refuses to capitulate, the grounding is going to go on, and the longer the grounding goes on, the more problems are going to be discovered, the more orders get canceled, etc.