on realpolitik grounds, Indianapolis would be a fascinating choice.
For all the home-grown developers, many would prefer to stay close to home than have to move to the mad-house of the coasts. In other words, I question that most developers would think the same way you do.
I'm not sure how we would scale for HQ2, however, but I believe it could be done.
Proximity to an international airport that can easily handle Amazon's shipments has got to count for something, right?