I agree with your points. But I stand by my statement that "If every last detail is what we seek, than a 20% or more increase in light gathering and resolving power should make a noticeable difference at the eyepiece...."
Very true. I guess just depends where one want the focus point to be at the moment. One thing that always makes me chuckle when folks scoff at optimizing to best eyepieces and to focus on increasing aperture instead is that it sort of leaves a current problem and lets it propagate to a new scope. Optimized components like eyepieces and diagonals seem to hold their stature for decades really. So the scopes/objectives really come and go over time, often moving up in aperture. However, the optimized accessories like the diagonals and eyepieces really stay around as the scopes change. So it that light they are a bit more important because they will bring their magic to any aperture one gets.
I use a 5" refractor. It is the heaviest scope I will ever want to lift up on its tall pier. My EP's are almost all minimum glass with the exception of a Nag 13mm T6. I choose the EP's that go as deep as possible.
I'll bet my 5" goes as deep as some 6" with lesser or more complex glass. I also use the best diagonal I can afford.
So, I figger I save my back and thousands of dollars. Far cheaper to optimize the rest of the optical train (as long as you stay away from wide-field mania!).