ibus
I was checking the web to see whether it’s possible to write an input method for SCIM using Python (the answer was yes), and I found ibus. ibus is a new input framework, by the author of SCIM himself. A particularity is that most of the core seems to be written in Python, which is interesting for such a low level thing as an input method.
Input methods like ibus-pinyin, ibus-anthy are thus written directly in Python. It should be pretty easy to integrate Zinnia into ibus then! (using the canvas widget provided by libtegaki-gtk)