Pablo: "That is out of contract and goes against the guarantees on the GC and can (will) cause the finalizer of the object to be executed more than once. I don't think is a good idea to expose an API that allows breaking the guarantees that we give: every object is finalized once."
I concur with Pablo. We must not expose an API to "unfinalize" an object.
Irit Katriel: "Can this be closed now? It seems that the query API was added and the set API was rejected."
Right. I close the issue as rejected.