You can never have too much info 
Here's an inspiration image of my outdoor staircase, the design that is:
And having an unfinished attic as storage shouldn't be a problem.
If you later furnish it a bit, the building committee need not care
And I want to recommend insulating the exterior of the roof overhang with foam plastic.
It keeps the attic dry and a little warmer, which is also good for storage.
http://www.thermisol.se/applikationer-losningar/isolering/takisolering
The staircase in reality:
Here's an inspiration image of my outdoor staircase, the design that is:
And having an unfinished attic as storage shouldn't be a problem.
If you later furnish it a bit, the building committee need not care
And I want to recommend insulating the exterior of the roof overhang with foam plastic.
It keeps the attic dry and a little warmer, which is also good for storage.
http://www.thermisol.se/applikationer-losningar/isolering/takisolering
The staircase in reality:
