Thanks for the feedback! I took the same road like Joel proposed (after making sure the mediator name is unique through createUID). I don't understand however that (Pure)MVC doesn't have support for something essential like this out of the box
My guess is that the framework is supposed to be 'as simple as possible, but no simpler' and this sort of solution is one that will vary from project to project. Using the Notification body and/or type parameters is effective for this sort of thing, so really it does support it out of box.
If you have a good way to plumb something up, you might consider writing a utility to do so. I'd love to check it out. I'm running through solutions in my head, but I get stuck at the way I've always done it (as described in my other post).