The rev. limiter in the ECU is really not intended for rev control as much as it is a measure to prevent over revving the engine.  In the case of the FAST system, it is a fuel cutoff with programmable parameters.  In my opinion, it is not a good idea to have the ECU do the rev limiting for a system designed to work with many different applications.  For instance, to cut the spark while interfacing to a Buick C3I module would cause the C3I module to lose synchronization with nasty results.  In my opinion, it's better to leave that to the specific ignition system.
Lance