A nice idea...but Earth/Luna orbit SPS are only 'uneconomical' to launch because we foolishly [as we've just seen again] buy into National AEROnautical and Space ADMINISTRATION paradigms of WIMPY and expensive ROCKET launchers.
Build Freeman Dyson's "Super Orion" [Daedalus modified to be eco-friendly].
EIGHT MILLION METRIC TONNES [about two orders of magnitude more than everything humanity has heretofore put into space combined] at 35 CENTS/POUND to orbit in 2005 dollars.
Put a CITY into orbit not a 'shuttle'.
Thousands of engineers and spacejacks with everything for initial stage of full space industrialization/colonization; permanent lunar base kit with miners, processors, mass drivers, construction-shack for SPS and Lagrange 4/5 O'Neill colonies with mass catchers, etc...basically the whole package that's been languishing since the Bicentennial...sent up in ONE Orion launch.
Of course we'd have to thumb our noses at neo-Luddite neo-Malthusian antihumans and tear up those silly little partial test ban and UN space treaties that you can be sure the Red Chinese wont let get in their way...but wouldnt it be worth it to advance humanity a century beyond where the lefties will let us be AND give America a REAL 'Project for a New American Century' as well as unlimited energy potential?