If with "out of the box", you mean the scenery will be already made using GSX Level 2 jetways and will include a proper GSX customization, you can do it very easily with the GSX editor and, as explained page 36 of the manual, the "Note for scenery developers" chapter, by supplying the GSX .INI file (or multiple .INI files, if you have multiple switchable AFCADs) in the scenery folder.
