I would be happy to move the python client to a separate repo. The only challenge is having access to the protobuf files during the code generation of the python files. This is trivial when they are in the same repo but takes a little more thought if they are going to be in separate repos (certainly still possible though).
As far as versioning in protobuf, protobuf tries to be forgiving across different versions of a protocol (https://developers.google.com/protocol-buffers/docs/overview#a-bit-of-history) and I haven't seen versions specified in protobuf files but I would be open to ideas such as adding a version field.
There are two main issues with Windows support currently:
Code generation from protobuf files
Link additional libraries (boost-fiber, boost-context)
The good news is that both of these are definitely possible but I unfortunately do not have any Windows machines. That said, if anyone is interested in adding Windows support to the revision, I would be happy to assist however I can