The existing behavior is what I'd expect.

Using python3:

>>> import ast
>>> s = open('file.py', 'rb').read()
>>> s
b'"""\nHello \\n blah.\n"""\n'
>>> ast.dump(ast.parse(s))
"Module(body=[Expr(value=Str(s='\\nHello \\n blah.\\n'))])"
>>> eval(s)
'\nHello \n blah.\n'

As always with the AST, some information is lost. It's not designed to be able to round-trip back to the source text.