Very interesting discussion.
My own take on this is that I tend to agree with the consensus view so far on this issue. There's just not enough of a draw to make a bridge between Bullfrog and Halls feasible (nor will there ever be), and just as importantly, Route 95 is a more direct way to cross southeastern Utah. If you're not on a beaten path, you've already got two strikes against you. No matter how shiny the bridge might be, unless you are intending to go to Bullfrog or Halls, there would be next to zero pass-by traffic on such a route. That's way different than, say, Moab, which is on a long-established regional route between I-70 and I-40. Moab, for its part, not only has the advantage of two adjacent national parks and the Colorado River, it had a baseline reason to exist in agriculture and mining. Also interesting that as crowded as Moab gets today, its permanent population of about 5,000 is largely unchanged since 1960--it had a baseline reason to exist other than tourism. It's the modern tourist infrastructure that has transformed it...and yet, the baseline population still remains at about 5,000.
You might ask, why couldn't the same thing happen in Bullfrog? It's incredibly difficult to start a town from scratch if its only purpose to exist is niche tourism. The cost of making a city grow from nothing is incredibly high, and extremely difficult to create the fabric that makes a city--public services, schools, grocery stores, support services, consumer goods, social institutions, churches, etc. Plus the extension of all the utility infrastructure. You really need a stable primary industry or two to drive growth and stabilize a population. That could be manufacturing, agriculture, or even government for that matter. Bullfrog/Halls would likely never have any of those things.
So then you might say, what about Page? That place grew out of nothing. Yes, but Page is a unique cat. It had a giant purpose--it was conceived as a massive glorified construction base. Page was literally called "Government Camp" at first, and administered by the USBR in its earliest days. It eventually transformed into being a city, but it took 6-7 years of constant construction--roads, the bridge, the planned city, the dam itself--and then the operation of that dam to to stabilize it and keep it alive. Page also had a built-in source of water and power thanks to the dam. It's instructive to see that Page's 1960 population of about 3,000 was sliced in half by 1970, as all those construction jobs disappeared. The population stabilized at only 1,500 by the end of the 1960s, even though it had a pretty solid foundational base of jobs related to the dam, lake tourism, government, and support services. It took the Navajo power plant built in the early 1970s to boost Page's base population to more like 5,000. The population has slowly climbed to be closer to 7,500 today as publicity (especially via social media) has created the demand for additional tourist-related support services. Is that a good thing? Debatable, depending on whom you ask.
Page was also greatly helped by its advantageous location as a transportation shortcut between Kanab and points east, a much more direct route for regional trucks than using the old slower route 89 (now 89A) over Navajo Bridge at Marble Canyon.
Is either the Moab or Page story remotely possible to replicate at Bullfrog/Halls? I don't think so.
It's also instructive to remember that in 1972, there was once a serious proposal to construct a bridge over the Escalante River in the vicinity of Coyote Gulch to link the town of Escalante and Bullfrog via an improved Hole-in-the-Rock Road. It was supported by some in Escalante who felt they needed some sort of economic boost that such a road link would provide. Of course it never happened. But imagine how it would have fundamentally changed the dynamic of the canyons along Hole in the Rock Road, and opened an industrialized tourism valve between Lake Powell and Escalante. We can debate whether or not that would have been a good thing, but its hard to argue that the remote character of the Escalante backcountry is a unique and irreplaceable public resource that would have been permanently altered...