Create a more cohesive message-passing system capable of handling refreshes and arbitrary events

[Foxinatel]

I'm mostly going to use this issue as a scratchboard for ideas I've had and new ways that we might possibly be able to achieve this.
Ideally a good message passing system:

• Should enforce rules about types at compile-time
• Should allow a component to send a message to another component without hard-references

[Foxinatel]

If we are to design a message-passing system that's capable of passing messages between controllers without any concept of hard-references, there's only really one way to go about that, and that's dynamically reflecting on types. (Let it be known I hate dynamic reflection with every ounce of my being)

[Foxinatel]

This means that somewhere we need to store what is essentially a Map<Class<?>, Controller>, or more likely a Map<Class<?>, List<Controller>>
This is the fundamental design in the current event bus system, but leaves a giant flaw in the fact that we get dangling references.
An object should unsubscribe itself from the event bus in the situation when it's no longer accessible to any UI elements, but as far as I can tell, there's no easy way to implement this, so we'll have to consider alternatives.

[Foxinatel]

One idea that I've been trying to exploit for a long time is this idea of creating a tree of controllers, at which point we can start enforcing better control flow.
If we state that each controller has exactly one parent, we can start to imagine a control flow where refreshing a parent cleanly refreshes all of it's child controllers.

[Foxinatel]

In order to stop dangling references, we need to make sure that a controller unsubscribes dead (or soon-to-die) subcontrollers. This is easy if we make the assumption that every controller has a unique class, because we can just store a Map<Class<?>, Controller> inside each parent to lookup it's children by their class.
Unfortunately we have some situations where we actually use arrays of controllers, like with RemoteController, which complicates things quite a lot.
A RemoteController, for example, should be able to subscribe itself to a parent alongside other objects of class RemoteController