Reading through issue MCL-5528 I applied the --workDir parameter to my Minecraft shortcut and it seemed to work as the original error went away:

The game directory is invalid or inaccessible.
Error details: The system cannot find the file specified
Filename on disk: .minecraft
Path: %USERPROFILE%\AppData\Roaming\.minecraft
Exists: directory

However, now I am receiving this error:

Unable to locate the Java runtime.
Error details: The system cannot find the file specified
Filename on disk: javaw.exe
Path: %USERPROFILE%\AppData\Roaming\.minecraft\runtime\jre-x64\1.8.0_25\bin\javaw.exe
Exists: file

(They don't actually display %USERPROFILE%, just making messages more succinct)

Is there a parameter for controlling the Java version that the Launcher uses?