ideas

Java -> Python seems easier than Python -> Java.

What I want is to read in bytecode files and convert them to bytecode in another
format. Certainly this should be relatively straightforward. I'm assuming the
compilers from source -> bytecode will have already finished dealing with the
complex stuff. If I believe that the languages are computationally equivalent,
then there should be no reason (that I am aware of) that a bytecode -> bytecode
conversion wouldn't be possible.

Java seems to be typed, whereas Python bytecode is not. Converting typed to
untyped should be fine, and actually might mean the resulting Python bytecode
could be provable type safe. Converting from Python to Java bytecode would be
more difficult, since there would need to be some type inference of the Python
bytecode. That sounds like some magic voodoo to me.

It might be optimal to create an intermediate bytecode representation that could
be used as a target from and to various other languages bytecodes. This would
optimally allow for arbitrary bytecode -> bytecode conversions, meaning one
could write a program in Java and have it run in YARV or whatever.