Type certificates for commercial airliners should expire after 30 years. After that date, allow any existing aircraft to continue operating but don't allow manufacturing of any new ones. The manufacturer should have to recertify and prove that the design fully complies with all current rules.

The original Boeing 737 design only took 4 years so that would give them plenty of time to work through any necessary design changes. And if pilots need to obtain a new type rating then so be it.