I have a few thoughts here.
First, the lower "bypass", KISS! If you build a wall of rock you are telling someone, here, climb this! A cement barrier would do the same thing I believe. A light weight wooden fence like the one in the photo would be best, IMHO. It will get knocked down, but easily rebuilt or replaced (and doesn't screem "climb me"). Then as Greg said, revegitate and Label.
Second, The Eagles Nest. In the photo Meat posted it is easy to see the damage caused by FEET going up the hillside to attach the cables of our winches to that poor tree. Is there a way to move the anchor down lower so there is no reason to climb the hill? And I believe the anchor point needs to be visable so people will use it and not the tree! If we can make it look nice it is a bonus.
Third, the anchor. What is the rock made out of at the Eagles Nest? I believe the anchor at Upper Hell. is drilled into the rock and cemented (glued) in place, but there are BIG rocks up there that are great for just that purpose. Can we drill a hole in any of the rocks and have it hold? Just an Idea.
Forth, the tree. IIRC, there were two trees there, the small one that is still there and a larger one down lower. I have no idea why someone would pull that tree out, unless it fell down across the trail and blocked the way through. Maybe that is how the "path" to the right got started. I don't know.
When the date is set I will try to be there to help with anything I can.