I printed out that article you posted. It is a real read all right. It will take me some time to get through it, but until then, there are some comments to be made from my very limited perspective. Think in terms of "space", and forget matter for a moment.
If space is infinite, then the universe is likely expanding into an infinite void. In this case I would have to say that Doppler is the most likely cause of redshift. Again, in my limited knowledge of this subject (and an oppressive tendency to think only with Newtonian physics), it would seem that both Doppler and space expansion represent similar phenomena. Does it really matter from the perspective of the observer how the redshift is generated - whether it is Doppler or expansion? Both would seem to have the same effect, and both could even be playing a role. So objects are moving away from the observer in both cases, only by a different mechanism. I don't see how either approach would effect the redshift, or how that redshift could define either mechanism (maybe something in that article I just printed out).
From a very simplistic view, the BB suggests that no matter where you are in the universe, everything appears to be moving away from everything else, and there is no center of the universe. This strongly suggests expansion of space. If, however, matter is expanding into an infinite void, it seems likely it would therefore have a point of origin, and an outer edge. I believe most high brows in Cosmology would suggest that this is simply not likely. It would require that our local space be the center of the universe. Otherwise, redshifts would not be the same for the most distant galaxies in all directions. Certainly our instruments are sensitive enough to pick up even a slight variance in such redshifts and none are seen, at least to my knowledge.
This is such a contentious issue that it is not possible for anyone to provide a "correct" answer. I would suggest if your considerations of the origin of the universe has a significant following of learned professionals, who can say that you are wrong? No one!
The following are just my previous thoughts on that idea as it seems to be quite a common suggestion. There's nothing scientific about what I'm saying, it may even appear like waffle, in any case, science about what's beyond the universe is hard to come by.If space is infinite, then the universe is likely expanding into an infinite void.
Yes, infinite, but definitely not void. Everything that exists has some kind of connection to something else, or a chain of cause and effect to it. If there where just one universe in a void it would not have anything to connect with, it wouldn't belong to a chain of cause and effect. there would have been nothing to give rise to its existence or reason for its existence. A void can't provide a reason or basis for anything. You would be left with the question why just one universe. It would either have had to come from nothing, or something had been sitting there for an infinite amount of time and then with no cause just decided to explode 13.8 billion years ago (the way out of that, is to invoke the cyclic universe theory, but that's just as bizarre anyway).
Also, I suggest the laws of physics don't allow one-off phenomenon, if something can happen once, then it can always happen. The formation of a universe is a natural phenomenon, so if one can form then there must be an infinite number given an infinite space.
With my also limited knowledge I would completely agree. No, second thoughts, they represent distinctly separate phenomenon but have the same result. No third thoughts, I think they have different results. In the case of doppler only redshift, the shift happens immediately and is only dependent on your relative speed and is independent of separation distance. You should see the same redshift from 1 light year away as 10 billion light-years, if you're still travelling at the same speed.Again, in my limited knowledge of this subject (and an oppressive tendency to think only with Newtonian physics), it would seem that both Doppler and space expansion represent similar phenomena. Does it really matter from the perspective of the observer how the redshift is generated - whether it is Doppler or expansion? Both would seem to have the same effect, and both could even be playing a role. So objects are moving away from the observer in both cases, only by a different mechanism. I don't see how either approach would effect the redshift, or how that redshift could define either mechanism
If the redshift were due to expanding space then it would depend on the distance. If you were nearby, space would not be stretched much, but the further you move away, the more space will become stretched, so you will see more redshift due to this effect the further away from the source you get.
So, if space is expanding, then I think you're right that it could be both playing a role.
Another thought comes to mind, I thought the Michelson and Morely experiment demonstrated that light wasn't travelling in any medium, so how come expanding space can affect it anyway, it must be travelling in something it can interact with?
As you can see, I'm in a pickle with this one, so please apply your limited knowledge to my limited knowledge, and let me know what you think
Got lots more to add to the rest of your interesting post, but I'll do that after I've given my brain a rest.