This framework has an architecture that Storage / Lock / ID Generation / Serialization are pluggable. Once I've made Apache::Session::CacheAny which glues Apache::Session Storage interface with Cache::Cache.
Then what I've made is ID Generation stuff. Ones using mod_usertrack and mod_unique_id for session ID generation. They are now on my CPAN directory.
Note: Apache::Session::Flex has some bugs, so should be patched with one included in both tarballs.