lutti.py

import argparse
import logging

VERSION = '3.0'
parser = argparse.ArgumentParser(description='Luttify your messages')
parser.add_argument('message', metavar='message', type=str,
                    help='add a Lutti to be Luttified')
parser.add_argument('-up', '--uppercase', action='store_true',
                    default=False, dest='uppercase',
                    help='outputs Lutti\'s message as it should be')
parser.add_argument('-V', '--version', action='version',
                    version='%(prog)s ' + VERSION)
parser.add_argument('-v', '--verbose', help='enables verbose outpus',
                    dest='loglevel', choices=['INFO', 'WARNING', 'ERROR',
                    'CRITICAL'], default='CRITICAL')
parser.add_argument('-d', '--debug', help='Lutti needs help!',
                    action="store_const", const=logging.DEBUG,
                    dest='loglevel', default='CRITICAL')

args = parser.parse_args()
logging.basicConfig(level=logging.getLevelName(args.loglevel))

d = { "A":"𝙰", "B":"𝙱", "C":"𝙲", "D":"𝙳", "E":"𝙴", "F":"𝙵", "G":"𝙶", "H":"𝙷",
      "I":"𝙸", "J":"𝙹", "K":"𝙺", "L":"𝙻", "M":"𝙼", "N":"𝙽", "O":"𝙾", "P":"𝙿",
      "Q":"𝚀", "R":"𝚁", "S":"𝚂", "T":"𝚃", "U":"𝚄", "V":"𝚅", "W":"𝚆", "X":"𝚇",
      "Y":"𝚈", "Z":"𝚉", "a":"𝚊", "b":"𝚋", "c":"𝚌", "d":"𝚍", "e":"𝚎", "f":"𝚏",
      "g":"𝚐", "h":"𝚑", "i":"𝚒", "j":"𝚓", "k":"𝚔", "l":"𝚕", "m":"𝚖", "n":"𝚗",
      "o":"𝚘", "p":"𝚙", "q":"𝚚", "r":"𝚛", "s":"𝚜", "t":"𝚝", "u":"𝚞", "v":"𝚟",
      "w":"𝚠", "x":"𝚡", "y":"𝚢", "z":"𝚣", "0":"𝟶", "1":"𝟷", "2":"𝟸", "3":"𝟹",
      "4":"𝟺", "5":"𝟻", "6":"𝟼", "7":"𝟽", "8":"𝟾", "9":"𝟿" }

def lutti_to_unicode(lutti, upper=False):
    logging.info("Luttifying message...")
    logging.warning('Using functional state of the art programming..')
    logging.debug('Entering lutti_to_unicode')
    return ''.join(map(
        lambda l: d.get(l, l),
        lutti.upper() if upper else lutti
    ))

print(lutti_to_unicode(args.message, args.uppercase))
logging.info('Luttifying complete!')
logging.warning('End of program')
logging.debug('Any bugs in this code are left as an excercise to the reader')

Formatando melhor e deixando a função mais desacoplada das variáveis globais:

def lutti_to_unicode(lutti, upper=False):
    """Luttifies a lutti."""
    return ''.join(map(
        lambda l: d.get(l, l), 
        lutti.upper() if upper else lutti
    ))

Aí tem que passar o args.uppercase na chamada

Feito!

(...) mais desacoplada das variáveis globais

A única global var é VERSION, o resto vem de args, mas eu entendi o que vc quis dizer ;-)