Lets try and get away from this 'Captain must sit in THIS seat' mentality. Captaincy has liitle to do with handling skills - sad to say it, but there are copliots who would run rings around most captains in this respect.
The only thing keeping co's out of the LHS right now is the prejudice and 'seat protectionism' of the old school brigade.
What arguments have been advanced against this idea? lets see:
Giving control of such an aircraft to someone with only 180hrsTT when the Captain can’t override them is not a sensible move!
The 'Captain must have overriding control' argument is nonesense. Half of all Nimrod sorties are captained by Navs or AEOs, who have NO physical control of the aircraft. Whatever your views on non-pilot captains, there aren't large, Nimrod-shaped smoking holes populating the Scottish countryside, so it cant be the huge danger that BEags et al suggest.
16B