Going over the Boeing 737 AEW&C specs, I believe neither Boeing or Airbus has a sufficient platform to support a future AWACS system and this is the very reason why the US had not develop a replacement for the E-3 even though it is 40 years since the first plane had been launched.
The E-10 M2CA was to be the USAF's next generation AEW&C, SIGINT, and SAR platform -- based off the boeing 767.
There were a variety of reasons why the E-10 was eventually cancelled, but I think the fact that it was based off the 767 platform is not one of them. In fact I would argue that having a larger platform for one's AEW&C is better than having a smaller one as that means more consoles, more power, more processing, more fuel and endurance, and more space for crew rest during missions.
The Europeans of course have the A330 which is a similarly sized platform to the 767.
The Indians are even developing an AEW&C based off the A330.
And I'm sure you're familiar with the JASDF operating their Boeing 767 based E-767 AEW&C.
The problem is amount of electricity that is required and redundancy. The radar systems requires tremendous amounts of it. The Boeing 737 AEW&C had to mount a special electric generator on to the the engines which is obvious looking at the huge bulge on the left hand side of each engine. This means if one engine fails although it would be able to fly would still have to head back to base since there is not enough electricity to power all the electronics within the plane. This would be a severe flaw during a mission critical situation.
There's no reason why additional power generation couldn't be mounted on a larger twin engine platform rather than a smaller four engine platform. In fact I would argue that having a larger aircraft with accompanying large and powerful engines are more important for an AEW&C than having multiple engines.
That said, there's no reason why powerful radars cannot be mounted on smaller platforms: such as the E-2, G550 Eitan AEW&C, or C-295 AEW&C.
The only way I can think of to negate this problem is to select a platform with more then two engines which neither manufacturer offers in the right size. Sure Boeing can offer the 777 but it would be too big for the mission meaning it would be more expensive in acquiring and require more fuel to run. Airbus only has the 380 which is even bigger than the 777.
The two companies would probably not develop a platform to meet AWACS requirements since it would not sell in the commercial airliner market so it would have to be a mass remodel placing three or more engines on present model or a mission specific platform which P-1 is the only one that fits the bill.
I'm not sure why you believe that AEW&C uniquely requires more than two engines -- an AEW&C needs redundancy and reliability as much as a tanker, as much as an MPA, or even as a long haul commercial airliner... and the proliferation of these platforms should be evidence for the reliability of twin engine large platforms for those missions.
A330 MRTT, KC-767, KC-46 are modern twin engine tankers, built in large numbers.
737 AEW, E-767, and India's new A330 based AEW&C are all twin engine AEW&Cs.
And of course the P-8 will probably be the most widely proliferated MPA of the 21st century, and it is twin engined.
I think there's enough evidence of the reliability of twin engine platforms to suggest that they are far from unreliable or insufficient for acting as an AEW&C.
As for the P-1 acting as an AEW&C -- comparing it to the likes of Boeing 767 are obviously unfair given P-1 has an MTOW of 80 tons, closer to the P-8's 86 tons than the 767's 143-200+ tons (depending on variant).
So really it is more fair to compare P-1 with the Boeing 767 as AEW&C platforms given their similar weight:
- P-1 does of course have four engines which gives it greater redundancy in case of engine failure -- but at the same time the sheer number of new twin engine military aircraft from AEW&C, MPAs, and tankers makes me think the twin engine option is sufficiently reliable for long endurance missions. Maybe JMSDF preferred having a four engine MPA for its own requirements, but USN is obviously quite happy with their twin engine P-8 and all the air forces which operate or plan to operate P-8s, KC-46s KC-767s, A330 MRTTs, E-737s, and E-767 (only Japan) seem quite happy with the reliability of twin engine platforms
- P-1 does have more engines, but does that mean more power? After all each of P-1's engines is only about half the thrust of a Boeing 767 engine. F7 turbofan has a thrust of 60kN while CFM-56-7 is rated at 120kN. I'm not sure how this translates to power generation, but I think it's a bit illogical to presume that just because an aircraft has more engines means it can generate more electricity. Engines can be more powerful than one another, and additional generators can be mounted within an aircraft if the aircraft is larger.
- P-1's four engines does come at a slight consequence in that it means there is more drag, and more maintenance to do compared to a twin engine platform. I don't know if the fuel consumption for four F7s is less than for two CFM-56s, but that's something to consider as well.
