Some more rambling thoughts:
The Intruder's sniper is pretty powerful but both teams can hit each other with the pistol because the distance is less than 65 meters. I kind of wonder what it would be like if the sniper was replaced with the banana sniper... And if so, how much ammo should it have to make up for the difference? This is probably a bad idea.

I posted four comments because there's a limit of one thousand characters per post.

Some rambling thoughts:
I'm having a hard time thinking about what else should be done. The zipline route is kind of like a fast-track to winning the round if it's left unguarded. The major risk and reward of being a sitting duck on the zipling is countered by the intruder sniper. The sniper can be countered by a player with a shield covering a teammate who shoots at the zipline. That strategy can be countered by people shooting at the shield guy from the bridge or the long way to get to the cliff. People outside on the cliff ledge are very vulnerable to grenades but are not likely to fall off, so a sniper can protect them from a guard who tips them over. It's so chaotic because both teams can get there very fast, shoot at each other very fast, and the actual amount of space is pretty cramped. I do seriously think that this part of the map plays pretty well.

Move the sniper rifle that has zero ammo to the guard spawn room. Having to peek into the crosshairs of an enemy sniper to get it makes trying to use it in a serious manner suicidal. The fact that it has no ammo is a good enough joke; letting the intruders know that someone picked it up isn't useful and making the guards risk their life for some peepers means nobody will ever use it. It's a pretty interesting alternative to the binoculars.

Alternatively, replace the guard sniper rifle with binoculars. Much more straight forward because it's a useful tool and I think it'll get used well. Especially when it comes to figuring out if the Intruder sniper is still alive or not.

Reduce the amount of CS gas that the Intruders spawn with by 1. Having 2 is too powerful when pushing down the hallway to get to the helicopter route. Just giving the Intruders 1 is enough. This might make solo pushes harder but pushing as 2+ intruders with so much extra CS gas is too powerful in my opinion.

This map is the Super Smash Bros "75 m" of Intruder. I think it's really genuinely horrible but it's a short map with some freaking insane choices that redeem it by making the gameplay wild. It's like hot and cold temperature shock. Tune it up a little and I think it could be a gem.

New Bopman map?