It's definitely not to a level of "comatose" - we see him move them both at the same time, he starts conversations in one form and ends them in the other form, etc., so they're both active bodies. However, he does mention that his attention is generally more or less only in one at a time - for example, when he goes off exploring and fighting in the vessel, he makes it a point to let everyone back home know that his dragon form will only be available to attend to the most basic matters, and they're basically on their own until the vessel gets back. As a note, he can pop the eye back into his dragon head, and the vessel is just presumably a giant lifeless doll at that point (however, he could not put both eyes in the vessel and abandon the dragon body entirely, AFAIK).

If making the dragon form smaller would help, I would be up for shrinking him? I'd prefer full-sized but I realize being that huge is a logistical issue, LMAO. Maybe 10 feet long instead of 40? Or the big form can only be accessed in certain scenarios, but is still affected by soul stuff/death/etc.? (and otherwise it's...idk stuck somewhere? in hammerspace?) Making it a straight-up transformation wouldn't be exactly kosher canonically, though dragon eyes have possessed regular flesh-and-blood people before, and I figure a little wiggling is ok for DWRP, haha.

Let me know if you want to talk more, I'm plurk at marvelousmith if that's better! Thanks for your help, I've been eyeing this game for a while. c: