John Strickland has some suggestions for in-LEO transportation:
One of the features of the original space station and shuttle concept was a space tug. The concept was called the S.T.S: (Space Transportation System), which would have allowed access to other locations in LEO (in the same or similar orbital plane) from the station. Such a tug would be able to capture large payloads, either modules or large cargo containers, and deliver them safely back to the station. The tug was originally in the post-Apollo plans, but by the mid-1970’s, like many critical components of the current Station, such as the Large Centrifuge Facility, it got chopped by budget cuts and budget overruns of other parts of the shuttle program, leaving just the Shuttle. Thus this component was lost long before the 1984 Reagan Space Station proposal. We still only have two components of what was intended to be a three-component system.
There were a few half-hearted attempts over the years to restore it (e.g., the Orbital Maneuvering Vehicle, which Marshall screwed the pooch on with, among other things, stupid requirements), but this hasn’t really been a serious discussion at NASA in decades. Yet it’s a key piece of the architecture for both LEO and BEO ops (a BEO version could be similar to the LEO one, except with larger tank or propulsion kits). And it’s all enabled by gas stations, of course. And these are all issues that Constellation, with its “let’s do Apollo again” mindset, completely ignored.