I have a couple of suggestions for InSim packets to do with the start lights.

The first is a simple packet to be sent when the Green Light for a race start goes on. This could probably be just an extension of IS_FLG with a new value for a Green Flag. If this were the case, then it could also be used to notify normal racing has started after the racer exits an area of the track where a yellow flag is in effect.

The second is slightly more complex in that sometimes we wish to be able to do a staggered start, which would require using an InSim app to set each racers initial lights to red, and then manually controlling when each racer gets a green light from within the InSim app i.e. using a 2-way packet, perhaps called, IS_LGT do :
* Calculate start times and put them into an array with PLID and start time
* Send a TINY_ using that array to set individual timers
* For each racer, as their start time comes up, InSim packet gets sent for Green light and green light shown to racer.

I can actually do this in an LFSLapper script, but am left to my own devices to show the racer their lights and do the time calculations. It's messy but it (mostly) works, so no great shakes if it cannot be done. Then again, it's not exactly for the layman.

An InSim notification of when the race starts (green lights shown) could easily be abused to offer perfect starts every race with a far better reaction time than a human.

Quote from amp88 :

An InSim notification of when the race starts (green lights shown) could easily be abused to offer perfect starts every race with a far better reaction time than a human.

Give it a half-second delay.

If everyone in the race is using the insim to do staggered starts, then everyone being a half-second late off the the line won't affect anyone's race, but it would stop a single racer using it for nefarious purposes.