As Einstein said, "Space is what you measure with a ruler."

Which is the ruler here? The speed of light, against which this expansion is measured, or the increasing redshift of the same light?

Using the inchworm crawling on an expanding balloon, both are metrics of space and they are being related to one another, so which is the denominator and which is the numerator?

The Doppler effect isn't caused by expanding space, but increasing/decreasing distance between the source and the receiver in stable space. The train tracks are not stretched by the train moving away.

Using the premise of Relativity to say the space itself is expanding, ignores the basic premise that the speed of light is measured as a constant to the frame. If it applies in this case, wouldn't the speed of light have to increase, as space expands, to remain constant?

I have been following the subject for forty years and in the 25 since this particular fudge first occurred to me, I get the same evasions. Either "go look it up," or "light is measured locally, while space expands globally." To which I point out it has to expand locally, in order to expand globally. The balloon has to expand under the inchworm, as well as everywhere else.

I've even had people admit I might have a point, but basically admit they won't agree, because, "that's just not the way it is."

I'm not a professional, so I don't have much skin in the game, so it's just a question of curiosity, but given the whole field is off in multiworld, multiverses territory and that doesn't appear testable, eventually some generation of theorists are going to come along, who don't want to spend their lives worshipping at the alter of untestable theories, then reaction will set in.