Interesting post, and I can align with much of it.
First point on Soundstage vs Imaging...
There was a truly awesome post about the Stax SR-007 comparing soundstage and headstage. The idea was that soundstage is more the ability to make sound project out to seem like it comes from a source further away from your head (like a headphone that sounds like a speaker over there, while headstage was more like imaging, the sense of how and where instruments within the audio are spread from each other. So, headstage is pretty close to imaging. While the author said the SR-007 has pretty average soundstage, it had superb headstage/imaging, and though he wasn't "in the room" the imaging allowed him to clearly "see the room" of the music (especially with his eyes closed).
Second, my first pair of great or "audiophile" headphones were Etymotic ER•6i IEMs. Hyper HYPER detailed, and playing a binaural recording will have simply astounding imaging. They would make it easy to concentrate on any particular sound, and tell where things are positioned relative to each other... Does that sound good for gaming to you?
If you think of the advantages of headphone listening over speakers — personal/private, portable, physically smaller, high value — an IEM basically takes all those values logically further. Now, I really LIKE soundstage and the sense of "being in/part of the room," which I think some of the best fullsize headphones provide a great compromise from an amazing speaker setup, and I'd still say the full size over ear headphones are my preference overall because of that, but IEMs are the ideal portable or isolated listening solution. Getting a closed headphone or the (IMO compromised) active noise-cancelling headphones is only a half-assed solution to the goal of isolation... Good IEMs can provide more isolation, are more portable, don't need batteries, (usually) don't have resonance issues, and the Balanced Armature models are like having mini planar magnetic headphones as far as quickness and resolution goes. If you get comfortable eartips, or custom IEMs, you have none of the weight/sweat issues of closed headphones.
If I was going to LANs, I would get CIEMs with a cool design (maybe my team/clan logo), and at home switch between full-sized headphones and the CIEMs. Philosophically speaking, The only time I'd like closed headphones would be if I was somewhere where I needed privacy, but I also needed to frequently be interrupted and take the headphones off & on again.