I am not sure what the consensus is, but I wanted to make a suggestion to remove the fence behind the rock.
For highlander and 6s - it essentially allows the sniper to have a sightline through main, pocket, japan, china, and connector while being easily protected and exposing very little of himself to the enemy sniper, which makes sniper v. sniper really difficult. This is due to the geometry of the rock and how 70% of the sniper's body is covered and how the sniper can easily rotate to watch any sightline based off comms. During sac waves, it is difficult to kill the sniper as you are betting on hitting a perfect splash on around the geometry of the rock, while also dealing with pyros, scouts, heavies, etc denying you while you are in the air. Thus, your only viable option is to win the sniper v. sniper fight, which already is a disavantage for the sniper that is not playing on rock as his body is fully exposed and has to deal with flankers/bombers, while the sniper on the rock can be protected by his team and his body is not fully exposed.
For 6's in particular - the biggest argument for keeping the fence behind rock is that it allows the scout to climb up the rock and have the movement to jump back between china, cliff, and rock to deny the soldier and demoman during the sac waves - an important aspect of the metagame in the gamemode. If the fence were to be removed, it would impact scouts as they cannot jump on the rock as freely as they can to deny the bombs, which would potientally make scouts weaker on the map (?). The sniper argument also can apply here in 6's as it would make sniper a bit worse, which is always good.
These are just my thoughts though. I would like to hear other people's opinions regarding this topic.