A nice point.... but I must ask a few questions. Your light rail, assumedly, will serve Amelia Island and Saint Augustine, primarily? On an existing train track? Is that really the path a commuter train needs to travel? Neither community contributes enough workers into Jacksonville proper to neccesitate a commuter train.
Jackonsville is a SMALL metropolitan community. Clearly, those best served by mass transporation would be those in the Southern Duval / St.John's / Clay county suburbs. I agree, the idea of a "high tech bus" is ridiculous. But aside from the very tenuous idea that St. Augustine is a commuter neighborhood of JAX, the needs of these residents simply are not served with a Amelia Island to St. Augustine train.
If it could be conducted very cheaply (less than $100 million) and sustain itself without city subsidies, it might make sense. I find that unlikely. In all reality, it will just be the latest incarnation of the Monorail, a silly mass transportation idea nobody uses for lack of sensible planning.
Perhaps I am a bit jaded, but having lived in absurdly big cities with far worse traffic, I find it a bit entertaining how a city of less than 1 million can seriously look at commuter trains. The idea deserves some study, perhaps, but I find it impracticle. Sadly, I cannot offer a better solution.