Using propertyChanged events means one event gets fired in the sender and a switch statement in the listener. I guess it's hard to make anything more optimal. A separate event for each property would get out of hand.

Using bindings within model/vm classes would be more simple than subscribing and unsubscribing to objects as they come and go.

Maybe something similar would work to push UI requests up to the UI layer. Another alternative is a static class to which objects can push requests and UI things can listen.