Hm, i think that is a little bit to much work.
For that you must create different scenes in Octane.
I can do that by save a scene from Octane with a simple cube in it.
If i want to render a alpha pass, then i give the scene a black background and the mesh a light material.
I use this scenefile as source and put it in the exporter. Here i can manipulate all lines i want, maybe to change the cube in an other object.
Or change the background color to white and the power of the light to 0, if i want to invert the output.
Then I write the scenfile from the exporter back to disk and tell Octane he should use this scenefile.
Same with the z-depth. For that i use a gradient image and change the uv-coordinates in distance to the camera.
It´s all possible but any changes from Refractive in the file-architecture will destroy it...
In other words, wait till it´s implemented
face