I'd prefer to have it just chopped into sections 4-5 minutes long and have them labeled a,b,c,d,e etc. It makes it easy to import a short section when you only need 30 seconds of ambience but then you can piece them together if you need long sections.
that's the kind of stuff we tend to bring loop group in for, as do a lot of places. As such there's probably a little less demand for library stuff than there would otherwise be.
Do you have access to a suitable recording space? You'll be waaay better off rolling your own with this type of thing.
I completely agree with the above. What can also be done from a very literal stand point is to rename specific files in your edit to basic names like Audio 01, etc. and even go so far as to compact your edits with super short handles (NOTE: Compacting should only be done to a saved out copy of your session).
If you're using multiple elements, even comp ...
I'd prefer option a), because I often end up with an ambience recording, that stops exactly where I want it to continue. It is a little bit more work, but in the end there is added value if you can decide by yourself where those representative sections are.
Another option would be to have markers in the recording that point out the representative sections ...