Jetpack idea...
Do you guys like this idea, does it sound like fun or should I not include it?
Only works when you're in proximity to an object that you can grab and climb on? Sounds more like a grappling hook than a jetpack to me, but no matter how you dress it up that can be a fun gameplay element, adding mobility to the player and opening up the map. I say give it a shot.
The jetpack was one of the funnest parts of Starwars: Shadows of the Empire for the N64. Really awesome game, overall.
Funny, I was about to mention the jetpack from Shadows of the Empire as well. The jetpack in that game had a limited amount of fuel. While in use the fuel would deplete, but when not in use it would slowly recharge. Consider using a similar mechanic. It prevents level design from being tossed out the window due to the player having too much freedom of movement.