Love to here everyones suggestions, I learn stuff from this as well BUT my usual though when ever anyone suggests how to do something I always think "halfway through turn 1 at Phillip Island and X happens.....how will that affect the car?". My thoughts are always with making sure your engine saving setups don't send you spinning off the track at 150kph.
A basic warning light before any cut/rpm limit/whatever may be much better than anything becasue it gives you time to set the car up for slowing down.
I have had systems setup on cars where it all gets a bit complicated for the driver when they are in the zone of driving......if they are a little unsure of what will happen they can loose confidence and therefore are ultimately slower. Somtimes you have to K.I.S.S.