It is already scriptable. Just not with one line.
font = currentDocument.font()
ufoExporter = Glyphs.objectWithClassName_("GlyphsFileFormatUFO")
ufoExporter.setConvertNames_(True)
ufoExporter.setFontMaster_(font.masters[0])
url = NSURL.fileURLWithPath_("Path/where/to/save/test.ufo")
ufoExporter.writeUfo_toURL_error_(font, url, None)