In order to help other people struggling with this, I am now answering this myself.
After some deep research I have now found out that it has not been possible to have any standalone python elements before gst-python 1.4.0 was released on 2014-10-20.
For the release notes take a look here:
http://gstreamer.freedesktop.org/releases/gst-python/1.4.0.html