On the question of Big country vs Small country, Canada is in the position of being militarily risk adverse and slow in procurement process. So much so that such a program like following India’s indigenous Awacs program seems like a step too far.
India is a bit of a different kettle of fish. They are non-aligned. They are the most populous country to have ever existed akin to the combined population of China and Russia. They can throw 10,000 engineers at an problem and work up and indigenous solution, which only they need to adopt. Their threat matrix is different. They typically do not do expeditionary warfare. They aren't in NATO. They aren't even US allies. They regularly operate Russian gear.
Not even the US could do the E7 in the time frame to make it relevant by itself, its a 20 year program that is maturing nicely. The 737 ended up being a good sized plane, slightly smaller than 707, but way more modern with growth potential over very cramped business jets and things like the E-2 Hawkeye. Japan had the 767 and ended up in an orphaned development that was more E3 than E7.
Boeing is a backlog but there really isn’t an alternative to the E7A in that high end available unless Airbus drops an A320Neo M3 AEWC in the near term (which I doubt will happen.)
Even then, that would not see the money, priority and effort being thrown at it as the E7 is. The E7 is filling in a USAF technological/ideological failure or misjudgment that satellites will replace everything. They can't, nor will they ever. The E7 development has been a trial by fire, on a very ambitious platform that is blowing everything else out of the water, and has proven itself within 4th gen and 5th gen modern peer battlespaces.
Its not just about size, or power, or range. Its about software and processing, and integration. You need something that can fly 500-100km away from the front line. No development of the fighter jet or space sats will ever replace that.
If you go Globaleye or similar, sure, there is some capability, there, but its very different. It is much more like the older E3 in terms of it being able to do some traffic control in the air, particularly for forces that don't have high level integration and ultra modern systems as small ops can be coordinated from that platform, but its not the same as the E7.
The E7 is a enabler of and order of magnitude greater. If you want to operate F-35's and low observable munitions in a battlespace, you will want the E7.
It also has way better endurance and operational tempo capabilities. 4 E7's would likely be able to operate more, cover more, control more, than 8-12 smaller AEW aircraft.
The 737 platform itself, is extremely durable and cheap to operate and maintain. The people thing is always a major concern, but the E7 requires only fractionally more manning, even with just 10 consoles, they don't all need to be manned. Which is another strength. Buy the plane, and there is already a massive pool of operators from Australia, Korea, Turkey, UK and the US to fill seats on any deployed mission. The computer systems are very much next level, with huge effort put on integration between systems like Aegis, Cooperative engagement capability, general battlespace management, F-35, weapons, ground stations, satellites etc. These are flying daily along Ukraine, along Turkish boards in the Mid east, along the Korean front line. Nothing from Europe offers that. Which is why NATO is buying E7's. How many global eyes are currently flying? How much money have they poured into the platform? How much combat has it seen? What is its development potential?
But acquisition costs are definitely a thing. But work share, you can basically do all of the refurbishment and fit out in Canada. The airframe is not the main game in this build.
If you want to increase Canada's aviation industry, get Air Canada to cancel 4 of their 737 max order instead, and buy 4 used 737's. Then force air Canada to buy and operate BG6000. This would also be dumb, but not as dumb as not buying the E7 because the Global Eye might have potentially, perceived, more workshare. Life time costs and operational costs would be likely greater on the Globaleye, while offering much inferior capability.
An E7 can remote fire weapons from fighters or ships, guide those weapons on complex trajectories to avoid threats and detection, while also scanning for drones and smart munitions, listening and then degrading enemy radars and communications on planes, ships and ground and space, while, moving at 900kmh, across thousands of km2 ever second with hundreds of aircraft in the air in a mix of military and commercial airspace, with essentially un-jammable coms/radar and do it for 12 or more hours, all day every day. From full high intensity peer war, to sanctions to just observation to intelligence.
It would be a very worthy area for Canada to throw money and effort into.