Вы имеете в виду что-то подобное?
>>> import itertools
>>>
>>> password = 'Dude123'
>>> charList = ['d8','vV','','D8','','','']
>>>
>>> finalString = [''.join(set((a, b))) for a, b in zip(password, charList)]
>>>
>>> possibles = list(''.join(poss) for poss in itertools.product(*finalString))
>>> possibles
['Dude123', 'DudD123', 'Dud8123', 'Dvde123', 'DvdD123', 'Dvd8123', 'DVde123', 'DVdD123', 'DVd8123', 'dude123', 'dudD123', 'dud8123', 'dvde123', 'dvdD123', 'dvd8123', 'dVde123', 'dVdD123', 'dVd8123', '8ude123', '8udD123', '8ud8123', '8vde123', '8vdD123', '8vd8123', '8Vde123', '8VdD123', '8Vd8123']