Crab -
oldman said "Just imagine another bunch of decision makers with little aviation knowledge and one eye on the budget between ARCC and the SAR Det"
Perhaps that's where the Scottish model fell down, and ours (so far) seems to work. Firstly, we don't have another bunch of decision makers - we have basically removed the original decision makers (ambulance service despatchers) from their control room and put them in with the aircrew. Masses of aviation, medical and local knowledge in one room. And secondly, (perhaps even more important) they don't have to worry about budget restraints.
We currently task our two aircraft in Yorkshire, plus GNAA's Teesside based 902 into North Yorkshire whenever they are better placed than us to attend. How far you could scale this up - for example a "North of England" AA despatch centre - is debatable.
Our Airdesk works because it is small scale and specialised. You could no doubt replicate it at the other AA units around the country given the will and the (not inconsiderable amounts of ) money required to introduce and man it.
At the end of the day, however, you would still be far from any type of centralised command and control of all the airborne assets.