I can't find anywhere in the documentation where type=bool, type=unicode or type=long are disallowed. They shouldn't be disallowed. If you want to pass type=bool, argparse should not stop you. And it currently doesn't:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=bool)
>>> parser.parse_args([''])
Namespace(foo=False)
>>> parser.parse_args(['x'])
Namespace(foo=True)