This was attempted before but failed -- any change requires tweaks to object-fusion. There are two options I have thought of, I strongly prefer (2).
Rename getValue method to value proxy -- effectively making the set('value proxy') become an override and making proxy become lookup. Not practical at all.
Inside of object-fusion, expose this.key and this.node on Fuser.
Don't forget about documenting new items inside of object-fusion.
Addressed in 3858c6f =)