I honestly REALLY doubt that thing on the mountain is for the Blimp...
First of all the Blimp's real life copy is the Good Year Blimp that takes of from Carson just off the 405 Freeway.
I posted this a looooooooooong way back some months ago.
Second what would a tour blimp do on the top of a mountain?
And do not know what it is worth but I wrote R* mouthoff to ask about the map and if they had actually shown us the entire map, and this was their reply:
Rest assured that what we have shown so for is just a glimpse at the massive city of Los Santos and its vast surrounding hills, countryside and beaches. There will be lots for you to explore for yourself come September 17th.
I have a feeling the awesome maps made are a bit off, I feel like we are missing something especially east-Southeast. I also have a feeling that the mountain in Question is not the far north.
I can't remember which page, as it has been a while since I posted here, but im sure we saw a picture that angled right showed that west of that mountain continues north.