Dear Juan,
I just re-read your essay (I had read it once soon after it came out but wanted to refresh my memory).
I agree with several of the eight points you made, and indeed some of them are quite close to the arguments discussed in my paper.
In particular, the idea that spacetime is not fundamental (or "special" as I like to say) would seem to be an unavoidable consequence of attributing quantum phenomena to the spacetime manifestation of objects that actually exist in lower dimensional analogs.
Also, I agree with the notion that unitarity is not fundamental, but it appears to me that this is for a different reason than given in your paper: In my framework, the mathematical requirement of unitarity arises ultimately from a simple symmetry that serves as a mechanism for comparing two distinct proper time dimensions: the proper time of the underlying onject in areatime, and the proper time associated with each path that is part of the path integral. Since objects we observe in spacetime do not require this "comparison mechanism" this would seem to refute the notion of unitarity being fundamental.
My knowledge of black hole thermodynamics is insufficient to be able to give sound evaluation of your argument, but let me just say that I am a bit suspicious about whether any of the seemingly reasonable assumptions that had to go into combining quantum theory with general relativity will in the end turn out not to be reasonable.
You raise an interesting point under your "quantum state vectors are not fundamental" section: If one has a multiparticle entangled state, how sensible is it to consider each describable by its own "state"? Probably due to my own prejudices, I tend to shy away from claims that descriptions that are even more mathematically abstract than this as being the "fundamental" description (such as the state operator in Liouville space) because at least in my view, whenever one abstracts, one loses some part of the thing one tries to model, and the extent of that loss defines how much less fundamental the abstraction becomes. To me, path integrals are the most fundamental description. They may seem abstract, but as far as I can tell, they are the most concrete models of quantum object in that they describe objects directly in spacetime rather than in some abstract phase, state or configuration space.
The point that GR is not an ordinary field theory is congruent with that presented in my paper, although again for different reasons. In my view, the notion of a quantum field captures in the greatest generality the idea that there is some lower-dimensional fundament from which spacetime is continuously emerging, and that close to that limit where, as it were, the "phase transition" occurs, there is a constant flux between the "phases" perhaps not so unlike what can observe in certain thermodynamic regimes. Since GR is about "equal dimensional" objects in relation to the observer's dimensional frame of reference, GR cannot, according to this view, be an ordinary (quantum) field theory.
Finally, I suspect that dark matter may be related to gravity somewhat as gravity is related to electrodynamics: In the proper limits there may be some similar or even formally identical relations (say, Newton's vs. Coulomb's law) which may confound our observations and lead us to believe that there is a gravitational explanation for it, but these might reflect totally different underlying conceptual entitities.
Milgrom's relation does not seem in contradiction with this view, for one could imagine an analogy in which Newton's law was replaced with a special kind of "Coulomb's law" that holds only under certain circumstances (e.g. it is only noticeable at very large scales, it is always attractive, it even holds for entities in which all electrical charges cancel etc. etc. ). I suspect that Milgrom's relation is something like this special "Coulomb's law".
Incidentally, if you did not see the appendix to my paper, you may find it interesting to see the proposed schema of the metahteory.
So, overall it seems that we agree on many of the points albeit for substantial different underlying reasons. Thank you for reading my essay,
All the best,
Armin