sawdin,
I am leaning more toward the fact that they just simply couldn't build something from scratch at an Air Force base. Logistically, it is just not possible.
Did they do their DD, I can guarantee they did. Just taking another example, the 2000 Tone Sea-Based X-Band Radar that United States is building. Why are they building on the east coast, Gulf of New Mexico, when the final destination of this mammoth is Alaska? And it would take them 7 month for the thing to float to its final destination after completion? Or why don't they build it in California when the trip will be much shorter? Everything comes down to the question: Does the logistics allow such action?
Just my 2 cents.