It is really hard to come up with any airline that would operate such a fleet, especially because Airbus has publicly said that they are not going to re-engine the A330. It’s an airplane that will never exist, so who could we expect to operate it?
There no doubt will be some airlines with split 737MAX and A320NEO fleets. American and NAS
are two. There will be more. I expect the Chinese airlines will end up ordering both and maintaining a mixed fleet. Other politically influenceable airlines in countries that try to remain neutral like Turkish likely will split as well.
I am under the impression that the A330NEO concept was invented by journalists and aviation enthusiasts. Airbus has stated that they are willing to invest in the A330 to increase MTOW and add sharklets, etc. If the question is who will order such an airplane along with the MAX and NEO, then I have to assume it would be from China. AA
and Norweigian have ordered 787s and don’t operate A330s. I think any enhanced A330 would be ordered by an existing A330 operator.
If you have never designed an airplane part before, let the real designers do the work!