DIS or HLA as a solution ?
Has anyone taken a look at the DIS (Distributed Interactive Simulation) or HLA (High Level Architecture) IEEE standards that address many of the problems raised here ? These are internationally recognised standards for linking human-in-the-loop simulations together. They are already used very widely in military & other large-scale engineering simulations (e.g. researching future air traffic management concepts), and have been for many years. Both NASA & the European Space Agency use them in their own simulations.