By programming it you can achieve anything. But I'm not sure whether there is an easy data-based approach. Thomas is the one who designed it, he will know more.
If you want to include a custom skeleton in a pipeline, you can also write a script in your target DCC tool (for example a python script when you are using blender) which adds your custom rig to the human. You can define the bones and vertex weights in a file and apply them. This is possible because you can exploit the fact that the human always has the same vertex indices.
A tool like blender even has a tool built-in to copy vertex weights from one mesh to the other based on vertex index, which allows very easy transfer of a rig without the need for writing a plugin. So you could define your own rig on a human model in blender, and then transfer it to any other human you export from MH with a few clicks.
See this post for more details:
viewtopic.php?p=21209#p21209