Very good stuff. The only drawback of this approach is that it must be limited to environments where the state can be stored to allow the time warp. When heterogeneous /hardware/ in the loop enters in the simulation, it becomes impractical because either the state cannot be extracted or because the ´discipline' required in the coding has not been followed (and sometimes cannot). However, the pattern of storing an 'antimessage' can be used to enable VCR forward / reverse during replay of a live sim. Very powerful.
Georgia tech at one time had code base based on these ideas as an HLA simulation architecture. I'm not sure if it is under active development still or not. If I remember right, it was free as in beer but you had to contact someone to download.
