I was dealing with the same idea.
@ldlework answered my question in this thread
From within your own module, you have the leftExpander and rightExpander members which will automatically be updated by Rack with the latest references based on position in the Rack.
However, if you wanted to communicate with distant modules, such that those modules are in line with your module, then you can indeed traverse the leftExpander / rightExpander chain to find the module you’re interested in. Since the members are public, the modules in between do not necessarily need to cooperate. Th…
I managed to find my module and cast it to access its members, but I had no idea how to deal with the threading problems so reverted back to a message bus.
Edit: Come to think of it… perhaps Little Utils Teleport In has the answer to your problem.