This rule, if adopted down to high school and age-group level, will effectively kill the event and severely damage the sport.
1. I'll start with my opinion that long jump parents and coaches are the worst. They are the most vocal and aggressive fans in the sport. As an official, I have only ever been screamed at or threatened by the aforementioned individuals. They always question fouls, demand courtesy measurements, ask to examine the tape, and file protests. It's non-stop, scary, and I refuse to judge long jump any longer.
2. Most other officials feel the same way. There is already a huge shortage of certified officials due to age and younger blood not stepping up to become officials. If LJ parents and coaches start beefing over every measurement ("Whoa! My athlete took off five centimeters behind where you placed the tape!"), the officials are going to quit in droves. No volunteer or low paid official should have to deal with that crap.
3. Lose officials or have violent confrontations at track meets, then LJ will no longer be offered or meets will fold completely to avoid liability.
Most coaches and parents at track meets are pretty chill except for long jump. If the take-off point becomes somewhat arbitrary and subject to a retiree's vision, then all hell is going to break loose. In some places, assaults or even shootings will happen. This isn't hyperbole. It's been getting worse for years as angry Little League parent behavior invades our sport.