Re: Some assembly required
" NASA refuted the LEO is halfway ... argument by considering $$$$ cost, rather than energy / weight requirements. "
For the purposes of the Space Race, they were correct, particularly given the issues experienced with docking and navigation demonstrated during the Gemini missions, the limited computer power available and the extremely high risks of the time (remember they were pushing the bleeding edge of oblivion on the moon missions, with QC that was dubious at times - the teardown of Apollo 1 and another capsule after the fire demonstrated how sloppily they were put together and Apollo 13's service module blew apart due to carelessness during testing of its oxygen tank during testing 8 years earlier (the heaters were left on overnight resulting in cracked insulation, the tank was simply put back on the shelf without being properly inspected, nor was it inspected when assembled into the spacecraft.)
For other purposes (regular trips to the moon, other missions to LEO, trips to other destinations) then having a platform at LEO is a cost saver.
However the platform needs to be "large enough" _and_ you need to have enough missions to justify building it. How large is "large enough"? How many missions do you need?
Is there a market for GEO birds large enough to fill a FH or BFR payload bay? (I believe there will be)