I personally agree with the intent behind #42's suggestion but disagree with the way to get there.
Sniper on rock is pretty damn powerful, but I would much rather prefer just adjusting the rock's geometry / size so that the spot isn't as powerful (but still an option) and so that projectiles/hitscan are easier to land there. Basically, expose the Sniper significantly more so that it's infinitely easier for the other Sniper to contest from multiple points (but still gives the defending Sniper a tiny advantage) and easier for him to get pressured/bombed.
...this is also admittedly likely more work than just removing the fence, but I think it'd be much better for gameplay overall than just removing options entirely. If the fence is empty it can also be pretty nice to escape on with cloak as a Spy since people don't usually expect you to jump on it and expect you to just stay on the ground.
e:
Shrinking the rock also shouldn't majorly affect any sightlines for defending Snipers since you can stand on boxes and see over the enemy's rock regardless.
e2:
Something like this for more visual oriented people: http://i.imgur.com/y4Nm4eI.png
Note: Nowhere near exactly spaced, it'd have to be spaced correctly to prevent crouched Sniper being dumb.
The main purpose would be so that if you're standing you'd have a significantly larger section of your body (and more importantly head) exposed at all angles, if you're in the middle of behind the rock you'd still have almost your entire upper body exposed, while on the sides you'd have part of your side and most of your chest and entire head exposed. If you're crouched you'd still be more exposed than currently at all angles (with the added downside of you're crouched so you can't move around quickly without standing which now exposes yourself).
Ideally if done properly this would still be a solid rotation spot for Snipers still but wouldn't be a consistent spot to just stand at for most of the game on defense anymore, while still having enough height that denying jumpers shouldn't be impacted significantly in 6s.