Jdiver makes some good points on the challenges of other models, but to me the difference is that had Boeing not been trying to cheat the system to avoid a new type, they would have better designed frame to not require so many workarounds. No doubt they could take 80% of the MAX design and apply it to a new frame and it'd be a great plane - with proper engine placement, ground clearance, etc that would eliminate the need for MCAS.