Expanding the width just means that the drivers are going to take that extra space and get violations on the new limit instead. Narrow the rumble strips and put grass or gravel right next to it so that going over is instant punishment and they are suddenly very capable of staying within the lines. As proven for corners with those hazards and the street tracks where the walls define the track limits.
Rule is fine, track might need more obvious hazards because apparently penalties aren’t keeping the drivers within the lines. Time to dig some gravelpits.