What underlying justification are you talking about and what do you understand by "the Copenhagen model" precisely? At least in the Einstein vs Bohr debates the one denying that QM could be a complete theory because of its non-locality was Einstein, I think.
> Einstein's refusal to accept the revolution as complete reflected his desire to see developed a model for the underlying causes from which these apparent random statistical methods resulted. He did not reject the idea that positions in space-time could never be completely known but did not want to allow the uncertainty principle to necessitate a seemingly random, non-deterministic mechanism by which the laws of physics operated.
The underlying assumption for Copenhagen was to try to preserve locality by assuming non-determinism. However, there’s no saving locality — and non-locality is enough to leave determinism — so there’s no reason for the non-deterministic axiom.
I think I also meant “definite” instead of “deterministic”, but it works out the same.
I found this quote from David Lindley in a review of Adam Becker's book referenced in this thead (http://www.math.columbia.edu/~woit/wordpress/?p=10147):
"The problem with Copenhagen is that it leaves measurement unexplained; how does a measurement select one outcome from many? Everett’s proposal keeps all outcomes alive, but this simply substitutes one problem for another: how does a measurement split apart parallel outcomes that were previously in intimate contact? In neither case is the physical mechanism of measurement accounted for; both employ sleight of hand at the crucial moment."
Copenhagen interpretation showed up when they were faced with a choice between preserving locality or determinancy.
They chose wrong — we know now QM is non-local, and that the underlying justification for the Copenhagen model is an extraneous philosophical proposition.
But much like an extra dependency in a software project, no one wants to remove it now that it’s used everywhere, and there’s a lot of “good enough” stuff using it.
That said, it seems to be one of the major impediments to a unified theory: by dropping the extraneous assumption, we have fewer things to reconcile with GR, and can start looking for GR geometries that have quantized non-local behaviors.
ie, dropping Copenhagen and giving geons another look is probably worth it. (And is basically what loop quantum gravity people are doing, as far as I can tell.)