Every time I land in Jax, I love that all you see are billowy, dense green treetops and then, far off in the distance, a lone click of buildings starts to emerge. We already have the largest urban park system, a built-in focus! I would prefer the parks/preserves be connected by public transportation and walkable paths where appropriate. For me, the city would remain on a low, personal scale; no more sky-scrapers, and the giant office buildings need to be shrouded by live oaks and magnolias (maybe some kudzu). I think the major neighborhoods (Arlington, Mandarin, Southside, etc.) could be distinct little enclaves with specific flair where you can truly live within a 5-mile radius and not have to drive across town to the big-box and are anchored by public libraries and civic centers/museums/higher-learning institutions, plus it's unique ecological feature. Neighborhood schools where students ride bikes or walk instead of buses. The economy is driven by transportation and logistics companies, educational institutions and research facilities along with great medical options for the snowbirds and half-backs. Bucolic, natural, unobtrusive, with a dash of modern and pinch of progressive.
Jacksonville should be the place you want to: have a picnic or throw a frisbee; cruise casually down the river on a hot day; crisp to a golden brown on beautiful beaches; meander down a sun-dappled sidewalk, under an archway of craggy oak branches and drooping Spanish moss: sit on your porch and hear the neighborhood kids giggling on a playground. A city that knows how to play with what they're given. In short, America's backyard. =)