I found your Dec. 1 article on adding a possible stop to the Green Line interesting. If the businesses near the proposed stop are willing to donate land and money, then the stop will not cost the MTA very much, and it would be a good idea.
However, I think that extending the line to the airport should be a high priority, even though it may be expensive. Around 45,000 people work at the airport. Since the Green Line only carries around 15,000 people a day, if 10% of the airport employees started using the Green Line, its ridership would go up around 30%.