Can I launch the File (Save/Open) Dialog from the command line?
This can be done using AppleScript, like in the question you linked to. Watch out, this is not the same as Automator.

Example script:

osascript -e 'tell application (path to frontmost application as text)
set myFile to choose file
POSIX path of myFile
end'


This uses the simplest form of the choose file command, and puts the result in the variable myFile. The result will be of type alias, which has a POSIX path property, which we read in the next line. The result will be written to stdout.

Look here for all the possible optional options to the choose file command. You can e.g. provide a custom prompt text, choose a default location, or only allow certain file types.