Quoi?
Ok here it is. The captain of an aircraft must be that individual who is best placed to guard the safety of that aircraft? A decent agrgument? So here we go; relate to the single seat model - The pilot is at the centre of the aircraft and as such is the first person to see a caption on the CWP or feel an incongrous malfunction in the aeroplane. As such, despite the the possible interference of anyone on the ground or in another aircraft who may be on hand to help or offer advice, the dude in the cockpit is the man who's decisions will be judged, analysed and praised or scorned.
The point is, no matter how many people sit in/on an aircraft, the dude with the stick is almost always the shortest path from problem to solution as he has not only the controls but also the sole responsibility of looking after the aeroplane, a skill he has been learning since day one of flying training.
Put simply, it's all well and good to try and justify how well crewpeople can make captains but if you don't have the stick in your hand and the CWP at your side then you are simply going to lengthen the process by which your crew will deal with problems, this overcomplication is almost an offence in aviation. The shorter the command chain, the better - this involves no-one telling the pilot what to do, only advising him as to the best course of action since he and his co-pilot alone possess the relevant skills to deal with the handling of the aircraft, as tought by a FTS which, if nothing else is designed to make aircraft captains.
Any suggestion that anyone other than a pilot should be captain is simply overcomplicating the process of managing an aircraft or insecure about how his position or is viewed.
It's much easier when there's no-one around to bother your little brain
Wings.