Jython is no alternative for me. Altough it would be the easiest I think. I will use CPython.
I found some interesting presentation-slides about mixing Python and Java from DLR:
If runtime performance and load performance is not critial a simple "java -jar saxon9.jar ..." commandline would also do the job.
I will take a closer look at JCC (which preloads the Java VM).
Hopefully I can share my experiences or maybe also a solution someday in this mailing list.