There should definitely be some introspection around what constitutes an aircraft type and what doesn't. Perhaps it would be better if manufacturers could have

There should definitely be some introspection around what constitutes an aircraft type and what doesn't. Perhaps it would be better if manufacturers could have more leeway in terms of redesigning newer models of aircraft without requiring retraining. Say e.g. if Boeing would make a completely different undercarriage to a new 737 so it was as tall on its legs as a 320. That would have meant the MAX engines could have sat more like on the legacy 737. Which perhaps would have been a lesser change to the system overall than the changes made on the MAX? (larger engines, different engine placement, systems to counter the behavior coming from the new engine placement and so on and so forth). I'm not sure what the solution would be here, but it seems like any time a set of regulations is rigid-yet-full-of-holes it's almost better if it isn't so rigid.