Easier said then done. Inspecting planes is job that requires a lot of skill and knowledge. Most of those people aren't cheap and they tend to work for airplane companies that need their skills and can pay their salaries. Which in the US means Boeing basically employs all the best people for this.
IMHO, the system actually works just fine. Accidents are extremely rare and companies tend to learn from them.
A better fix would maybe be to just make it really expensive for Boeing to cut corners here and put mechanisms in place to verify that they aren't. And you could argue that is the case already. Their reputation suffered and it probably shows in their order books. So, I'm guessing they are very eager and well incentivized to move on from that.
And looking at the Airbus and Boeing stock price suggests that Boeing stock has never recovered from that. Both stocks went down a lot at the beginning of Covid. But the Airbus stock has basically recovered from that and Boeing hasn't.
Even the mere threat of regulators getting more strict is probably making investors really nervous. That could end up being more effective than any actual inspections.
Inspecting planes does require a lot of skill and knowledge. But one doesn't need deep expertise to detect loose bolts.
My experience is that when quality breaks down, the effects are visible at multiple scales and multiple places. Who knows what else is non-compliant in the 737 MAX assembly line (surely this is why the FAA announced an audit).
For all the criticism the American aerospace industry gets, Boeing is the only one clearly suffering the problems they have. If stricter regulations mean Boeing can't do business, tough luck.
Boeing's entire business is to make good aircraft, and they are grossly failing to do so; their problems extend far beyond just the 737 MAX. A business that can't sell good products shouldn't be in business one way or another.
Do it.
Do it now.
Sincerely,
Everyone