Even with crossfeed its not like a speaker. Crossfeed makes a really slight difference and gives a slight feeling of central image, its not a drastic improvement. With speakers you get such illusion of central image (or any other part of the soundstage), you can touch the spot in the air where the source of the sound would be. When listening to music on my Kef Q300's, I can put point my hand at each exact point where each sound is coming from, and with extreme precision, I can cover the vocalists mouth with the palm of my hand so to speak. On headphones, even though you get a feeling of where each sound is coming from, its never as exact or separated from the rest of the sound. Its just how it is. If you have a chance to do a direct comparison, do it. I can plug my headphones into a speaker amp and sit on the speaker sweetspot, and then play music and have someone plug in and out the headphones, so that I switch between headphones playing and speakers playing. Its such a huge difference in soundstage.
So theoretically, I agree with you absolutely... 100%. But here's the thing: Unless you have a dedicated listening room that you can outfit exactly as you see best fit, you have a much better chance of BETTER creating such an ideal space via headphones and various ancillaries including crossfeed. That's how I've come to head audiophilia. At first I didn't get it but then somewhere along the way the light bulb went on. I can come much closer to creating my ideal in every respect in head-fi. And not only that, I can have it be fairly portable to boot!