I'm not sure how SJTC got to "rail to airports," but I'd like to just add a really great example of a city, on a similar level with JAX, that has done this effectively.
Portland, Or./ PDX is a a little distance outside of the city and is surrounded by industrial and commercial development. A traveler can take the MAXX (a light rail) for approximately $2 from PDX to Pioneer Sq., which is in the center of downtown. The ride takes about 30-35 minutes, but the scenery is enjoyable and the cars are comfortable. The ride takes you through commercial, rural, and eventually urban neighborhoods with many stops along the way.
I think that JAX should look to this great example.