@Aleph0
"We can't, because shuttles haven't got solar panels. Their electricity is provided by fuel cells, which entails their max autonomy is about two weeks; in the '70s energy efficiency wasn't a major project consideration for crew-carrying space vehicles."
I thought this also. It is no longer the case.
"A shuttle could probably be made to work with a hookup to the ISS power systems,"
This *does* exist and the Shuttle is modified to use it, but it came late to the party The burn to undock and trigger reentry comes from storable propellants and they have on orbit storage for *years*. Likewise the APU's that drive the control surfaces use a storable monopropellant.
*But* the electrics, including the flight computers run off those fuel cells. US crewed spacecraft have *always* used H2/O2 fuel cells since Gemini as they supply drinking water and it's quite a power requirement (9-12Kw on takeoff/landing IIRC) to keep up for up to 14 days.
That would make Shuttle problematical for emergency undocking/return to Earth.
I'd like to think a modern design would make different trades. NASA *should* have either learned to get comfortable with *long* term on orbit cryogenic storage or gone the other way with a direct drive electrical generation system off a mono propellant APU, ideally with electric actuators (you might like to find a report called "The electric shuttle" written in the mid 80s). Note that Hydrogen peroxide *is* such a monopropellant but can be catalytic ally broken down into water and Oxygen. It's dense and *relatively* safe to handle (heavy rubber gloves and overalls, not nerve gas proof suits and separate air supplies). The boiling hot O2/steam mix coming from a cat pack is hypergolic with pretty much any reasonable hydrocarbon.
However it fails the NASA "Performance uber alles" test being inferior (but currently 6x cheaper) than the nasty MMH/NTO/UDMH stuff Shuttle uses for it's different systems.
Solar panels are a red herring. A Smart car battery pack could do the re-entry (but *not* the on orbit power and NASA would worry about "But what if you can't open the cargo bay doors, you'll run out of power with no way to recharge the batteries for the reentry".
The development of Shuttle systems really failed to find or use *any* cross sub system efficiencies.