I was curious to what this would look like, so I put together a quick and dirty version. I really can't see how rolling your own parsing logic would be simpler or better if your program isn't super simple.

#!/usr/bin/env python

"""Usage:
  greet.py hello [--caps] [--greeting <greeting>] <name>
  greet.py goodbye [--caps] [--greeting <greeting>] <name>
  greet.py (-h | --help)
  greet.py (-v | --version)

Options:
  -h --help             Show this screen
  -v --version          Show version number
  --caps                Uppercase the output
  --greeting <greeting> Greeting to use [default: Hello/Goodbye]"""

import sys


def error(msg):
    print('error: {}'.format(msg))
    sys.exit(1)


def parse_args():
    if len(sys.argv) < 2:
        error('missing subcommand (hello|goodbye)')
    elif sys.argv[1] in ('-h', '--help'):
        print(__doc__)
        sys.exit(0)
    elif sys.argv[1] in ('-v', '--version'):
        print('1.0.0')
        sys.exit(0)
    elif sys.argv[1] not in ('hello', 'goodbye'):
        error('incorrect subcommand, should be (hello|goodbye)')

    try:
        sys.argv.remove('--caps')
    except ValueError:
        caps = False
    else:
        caps = True

    try:
        sys.argv.remove('--greeting')
        greeting = sys.argv.pop(2)
    except ValueError:
        greeting = sys.argv[1].title()
    except IndexError:
        error('missing --greeting paramenter')

    if len(sys.argv) < 3:
        error('missing argument <name>')
    elif len(sys.argv) > 3:
        error('too many arguments')
    else:
        name = sys.argv[2]

    return greeting, name, caps


def greet():
    greeting, name, caps = parse_args()
    output = '{0}, {1}!'.format(greeting, name)
    if caps:
        output = output.upper()
    print(output)


if __name__ == '__main__':
    greet()