Taking a step back, let's look at why non-cosmological redshift is such an item of speculation.
The current mainstream model proposed a universe that is accellerating in its expansion, composed of 70% dark energy, and was home in the very, very early universe to a huge number of stunningly large quasars. These predictions date back about thirty years, before which neither dark matter nor dark energy were predicted, the universe was known to be expanding but not accellerating in its expansion, and quasars where little known. Also, the accepted value of Hubble's constant has been revised beyond the error bars assigned to it several times since Hubble first identified the phenomena.
A less than an order of magnitude change in the Hubble constant from 70 +/- to about 50 would bring the estimated amount of dark matter in the universe from 70% of all matter-energy to zero. Similarly, slight tweaks in very high z redshifts would eliminate the current mainstream prediction that the expansion of the universe is accellerating and would have an immense effect on the predicted size of quasars. The data that give us these values are primarily redshift data.
High redshifts, by definition, involve scales well outside the range of ordinary experience, even within astronomy. Andromeda, for example, is far closer than high z objects, yet we are still making major new discoveries about Andromeda.
I also have to agree with turbo-1, that the physics community itself, by widely considering ideas like M-theory, SUSY, branes, and CNS with only a weak phenomenologial basis, has lowered the bar to consideration of new physics as a possibility. When 11 dimensions, dozens of new undiscovered particles, and countless worlds with different laws of physics are on the table, it is hard to consider new physics that would slightly tweak very large scale redshift data all that remarkable.
This doesn't mean that alternative theories are right. But, I don't think that the concern that many people are throwing stones, while few people have complete alternative solutions is a fair criticism. The default position in science is "we don't know." The person who discovers Brownian motion or the photoelectric effect need not be the same as the person who invents quantum mechanics to replace it. The claim that dark energy makes up 70% of the matter-energy in the universe is an extraordinary and recent claim that calls for extraordinary proof. The proof supports this claim within the existing model, but general relativity is less well validated at a cosmological scale than it is in other situations, and the FRW equations which are central to this prediction may have assumptions that are sufficiently wrong to make a difference as well. The developments in cosmology in the past thirty years have produced claims sufficiently extraordinary that casting about for alternative models is in order.
