I think a lot of the problem here is that all of the forward looking design is looking at the 787 dreamliner where the air conditioning is done electrically rather than with bleed air. It seems entirely plausible to me that this situation arose due to a descoping halfway through the project, where an initial version of the design wasn't going to use bleed air, they then decided that doing that much design work would be expensive, and put the bleed air system back in "because it's exactly the same as what we've been doing for the past 100 years" and no one realized that in the meantime, someone else on the engine team had designed a system that would dump a couple gallons of oil into the bleed air system if there was an engine failure.
The air handling is exactly the same between the various 737 versions. The difference is that the engines are different. The CFM Leap is designed to shear the bolts on the fan if it goes sufficiently unbalanced, and incidentally the shock of this causes an oil leak. The A320neo will have a very similar problem of filling the plane with smoke if the LRD shears the fan bolts. It just does the air handling slightly differently, so it fills with smoke slower, and the entire cabin, rather than the flight deck first (if it’s the left engine that fails).
Nah bleed air is a pretty major system. 787 was a ground up design, so benefitted from lots of new tech. 737 max was something that they hoped wouldnt need a recert.
