Great story. Subscribed.
And it's hard to answer "why a wagon" if you don't like wagons. At the end, the response will be "yeah, I guess I see this and that, but still don't get it."
It's a personal preference as mentioned above and we can rationalize it whichever way we want.
To me, coupe is the most beautiful automotive form. But it's not practical, so the next best thing is a wagon. Hatchback works too, but has less space and wagon (to me!) looks nicer.
Plus you are carrying around the same footprint as a sedan, so you might as well use the air space above the trunk of a sedan for something useful!
And yes, I don't like SUVs. As a Sport Utility Vehicle, they do not have the "Sport" of a hatchback, they have the same "Utility" of a hatchback, and as a Vehicle, they use much more material to achieve the same utility and less sport. They weigh more, so you need bigger everything (brakes, suspension, stiffness material etc.), they ride higher, so you need bigger wheels, tires etc.
Again, personal preference, so that's how I rationalize it.
Now, let's resume this excellent build direction!
I'm watching intently to see what I can learn and adopt to my E91 ownership.