I Just hope We Will be able to use the climbing hook where ever we want. Such a feature Was possible in " Just Cause 2 " many years ago. ..so it's possible for FC4
( in this video an infinit Distance MOD for the hook but in reality the hook could reach +- 40 feet )
Here is a presentation video. ..
They already discussed this, they said that at first they had it so that we could use it anywhere but it didn't work out (I guess they might want to filter you to different locations and you could bypass areas and miss out on things maybe if you could use the grappling hook anywhere)
So now there are areas wher you use it, when on the hook you can go up / down and left / right or you can swing across gaps.