I like this a lot.
I hear what you're saying about bricks being unsuitable for horizontals, but I still like it. Maybe they should be just straight up stone block? It's not without effort – you still have to cook cobble to get it – so I could see it being used by a Lost Civ People or something. Plus I loves me a smooth span.
Not sure about the center path... fine if you're riding or footing it out there as long as you pay attention, but what if I want to bring my dogs? What if I find a rare zebra out there and want to leash it back to town? We all die, that's what.
I think there's something to Turtle's center glass idea. Not at rail level, but a block below. Could be right on, especially with our 'clear' glass texture.