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Yes, Python must be compiled with -fno-strict-aliasing (or
moral equivalent).

No, that's not going to change before Python 3000 (if even
then).  All Python object structs conceptually extend the
PyObject struct, including (but not limited to) object
structs conceptually extending the PyVarObject struct (which
in turn conceptually extends the PyObject struct).  This is
uniquitous in the core source code, and in all 3rd-party
extension modules defining new Python objects in C.

Note that Python doesn't much care about C99.  It was
written against K&R C, and went nearly a decade before
requiring C89 (it took that long for C89-conforming
compilers to show up on all interesting Python platforms). 
Best guess is that it will never require C99 (because best
guess is that C99-conforming compilers will never show up on
all interesting Python platforms).

That said, I don't see anything to object to in adding
fiddly casting patches to make sure compilers don't try to
exploit the trivial optimization opportunities that assuming
no aliasing in the Python source may allow.