Yes, welcome into the strange world of AIX...

You can allow up to 8 segments, which represent 2GB:
http://publib.boulder.ibm.com/infocenter/tivihelp/v2r1/index.jsp?topic=/com.ibm.itame3.doc_5.1/am51_perftune113.htm

We could change the option to become:
--with-aix-maxdata=value
where value could be between 0 and 8, with a default at 0 (nothing passed to the compiler).

Would that be OK with you?

The good news is that thanks to this patch I was able to play the full python test suite on AIX:

313 tests OK.
8 tests failed:
    test_asyncore test_cmath test_distutils test_fileio test_locale
    test_resource test_time test_wait4
16 tests skipped:
    test_ctypes test_curses test_dbm_gnu test_epoll test_gdb
    test_kqueue test_largefile test_ossaudiodev test_pep277
    test_startfile test_tk test_ttk_guionly test_unicode_file
    test_winreg test_winsound test_zipfile64

Not too bad.