You know this is funny to me. I compete predominantly in jumpers now and the warm up is effective for what it is. USUALLY the trainers are controlling the fence and dictating what the rider warming up does. There are multiple “fences” with enough standards and poles to make anything legal.
Now as a former eventer I still usually warm up without a ground person but I ask if I can share a jump with people and either explain I am alone, or point out any minion I might have who can help put a pole back as needed.
I still event a bit and I’ve seen scary warm ups at events as well as at shows. I think the compulsion to over warm up is the issue that causes the worst episodes that I have seen.
Especially for eventing it really is important to teach riders that less is more. You can’t fix all the problems in the warm up, but you for sure can cause more issues and expend useful energy that you and your horse might need if your attention to fitness preparations is lacking.
I would think you would see more success if you tried to have the situation where people do “have dibs” on a fence so that people can warm up for themselves and their animals more how THEY need and less about “I had to jump a max square oxer because I had no one on the ground and we nearly died!” It really is just about owning your choices, at least imo.
Em