My only access is a hotspot, I could use it to download after activation ...
As I install it to my netbook, I will use an usb key so I maybe be able to add some stuff needed to it ...
You may want to check out CrunchBang.
CrunchBang is derived from Arch Linux, with Openbox as the default window manager. Head to their website, download the ISO, burn it to a CD/DVD (or setup a bootable USB with it). Using that you should be able to install Arch Linux with Openbox without an Internet connection.
Hopefully, the Broadcom and ZyDAS drivers will work out of the box - if not, you may have to tweak them later.