Be able to have grapple points on stuff like ledges, helicopters and maybe even buildings. To ascend to one of these grapple points you would need a grappling hook, which can either be an item you find or just a passive item like it is in FC5. (Personally, I would like it to be an item.)
The player will also be able to attach two points together (if not to steep or far away) and create a zip line which can be traversed by any player.
This would allow the player to evade fall damage in another way than opening their parachute if they’re 15m off the ground, allow scaling up surfaces without requiring something like a vehicle or stairs and make up some pretty fun challenges for players exploring places like destroyed buildings.