The idea is good, but it would take quite a bit of programming to make it work.
First of all you'll need to program the trigger for the Safety Car, e.g. what would cause a SC. Five cars off the road? Three damaged cars? Two cars up-side-down? Then you'll need to tell the Safety Car when a driver is back on the pit straight, so it can intercept them (this could be difficult, as there's quite a speed difference between a Midget and a Formula Gran Turismo, there's pit stops etc.). Then you need to program what it would take for the SC period to end, which again depends on many factors, as a too short period can mean even more carnage, and too long a period means the 5 year old kids are going to get bored (they will be after one corner, but..). Not to mention, the AI will have to stay behind the SC and know when to begin at race pace again and penalties for overtaking the SC should be implemented as well, both on- and offline.
It was easy enough to do in GT4, as it was basically rubberbanding. The faster you were going, the faster the SC would drive.
Besides,
it's easier for all this way (shameless, free advertising

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