I don't think this should happen by default.
but what the user wants is already possible, by using the from_param() method.  For example, the AutoStrParam type converts everything to a string (and a char*):

from ctypes import *

class AutoStrParam(c_char_p):
    @classmethod
    def from_param(cls, value):
        return str(value)

strlen = cdll.LoadLibrary('msvcrt').strlen
strlen.argtypes = [AutoStrParam]

print strlen(None)     # "None"          ->  4
print strlen(type)     # "<type 'type'>" -> 13