I would also really like to see this back in the game. They did add it in GT5 so I am thinking there is a good chance. Hopefully we will get it soon.
Lagging is an issue as mentioned above and this feature can also help eliminate the issues of the punters coming in to just try and knock people off the track. I would use it in any public lobby I open if it were there. Without it I just avoid opening a public lobby most of the time.
It is probable that the idiots will leave when they see that they can't smash people of the track, so it will raise the quality of the room.