I like Enigma's "focal point" thought. I've tried to pay attention to the progression paths of the characters... and can report that much is left unseen and unexplained.
Here's a great example by way of question:
Whose pod is sequestered away in a District 04 courtyard?
Either I have blatantly overlooked something, or you can not support your answer with in-game proof.
...but getting back to Enigma's interesting thought. Let's attack the low-hanging fruit. Dutch appears on the ground outside District 09 and literally lands right in the middle of a District 09 plaza. The next time we see him, he's meeting up with Mickey in District 10. We could probably safely
assume that he had to travel through (at least) District 06 even if he used locked District Door 0906-A (see my
map). I don't like to assume. For all we know, he hitched a ride on a passing Phantom.
If we go with what we actually see in-game, we're left with three areas that we can't directly access via Mombasa Streets:
- High above the NMPD HQ in District 03
- The "Sunken City" beyond Kikowani Station
- An exit off the Coastal Highway in District 01
If Enigma's idea leads us to the answer, we're already looking in two of the three most likely places.