The idea is to reduce as much as possible
any entangelment hazard. What you propose (to remove your head) would certainly reduce entanglement risk, but for many, it is a detriment to safe diving (however, I have seen some where it is a definite improvement). While given that, in early stages of learning it seems easier to don/doff stages with a rigid d-ring, the truth of the matter is that it is a greater entanglement risk than a d-ring that will lie nearly flat against your chest, however small that increase, it is an increase never the less. And although you may make a large percentage of your dives w/a stage, the idea behind DIR is do it the same way ALL of the time. With or w/o a stage. Keep your rig as tight as possible. Rigid d-rings that stick out are just not as tight as a d-ring that lies flat. Tiny details like this is what set's this system apart. They have been developed by those w/much experience in tough environments for long durations, much more that most of us will ever have the opportunity to do and actually put these deatils to the test. I personally, trust their recommendations over those whose experience is really not comparable.
The learning curve is not tough on this one, take some time to practice and do it right...don't look for gimmicks to overcome a bit practice and training.
We don't neglect the details like this just because in our limited experience we have not run into a situation that would warrant such attention to detail. One aspect of DIR (and as I said earlier, what sets it apart) is this kind of attention to detail and reduction, as much as possible, of any entanglement hazard, however tiny or small. The beauty of it (DIR) is in the details.
Brandon
www.scubaguys.com