The essential premise of relativistic spacetime is that in a moving frame, both the ruler and the clock dilate equally, such that the speed of light always measures C. So there is always only one metric of space, the speed of light.

Yet to explain cosmic redshift, this is turned on its head. Presumably space expands faster than light speed, causing it to be redshifted. Consequently there are two metrics of space, one based on the speed and one based on the spectrum.

Given they must be related, as they are based on the same light, which is the numerator and which is the denominator?

If light speed were the numerator, it would be a "tired light" theory, but as it is an "expanding space" theory, the speed is still explicitly the denominator.

Beyond all the further complexities and patches to make it work, the entire theory is based on a fallacy.

It's like,"We have this great theory, but it only works if 1+1=5, so lets just make 1+1=5 an axiom and not worry about it."