A slightly different view.

[jlknapp505]

I came to some of the same conclusions that you've arrived at, but from a different perspective.
One conclusion is that the limiting velocity of light, C, is not a limit at all. It's simply the transmission velocity of the matrix of fields that make up space.
A second conclusion is that light, like all waves, must have a medium to travel through. This medium must have at a minimum elasticity; otherwise the negative portion of the wave couldn't exist. Light (and all other electromagnetic radiation) propagates through this medium as a disturbance in the medium, beginning as a "positive" energy input, and then as the energy diminishes, becoming neutral (ground or undisturbed state) and finally swinging "negative" due to rebound of the elastic medium. Evidence for this view is found in the dark/light bands of the familiar paired slits interferometry experiment.
A conclusion from this is that light is a variable, not a constant, varying with the density of the medium (hereafter called the Matrix; you may use whatever term appeals to you.

I came to this conclusion by trying to understand Einstein's view that gravity "warps" the structure of space/time around any material object, such as a planet. In order for this to be true, space must HAVE some structure. So I wondered what the structure of space might be; what's out there, between the galaxies and stars and planets?
The answer is gravity; gravity, and also electromagnetism, permeates the known universe. There are also particles, or standing wave interactions if you prefer. Particles seem simpler to me, at least for now. These particles inhabit a locus which is a concentration of gravity and electromagnetism, and these allow the particle to interact with the larger matrix of fields from major concentrations such as stars or galaxies.
Does gravity interact with light? Yes, proved experimentally by the observation of deflection of light (during eclipses) and later by detection of gravitational lenses.
Apply Newton: if gravity fields affect light, then light must also affect the gravity fields. In this way, the disturbance that is light transits the medium of the matrix of interacting fields that exists throughout the universe.
A strong gravitational source distorts the matrix more than a weak source, and this distortion varies inversely with distance. Interaction with light causes the light waves to deflect, or change direction slightly. Apply this same principle to a crystal, in which the matrix of interlocking fields varies with the structure of the crystal, and the light waves bend or sometimes split into two separate waves. Extend this further, and ALL waves can be explained by energy impacting on the various fields that surround all matter.
So: is light the fastest thing in the universe? Not necessarily; it's just the interaction of energy with the fields throughout the universe, and as such is limited to the propagating velocity of the matrix. Sound waves in air or water are limited to the propagating velocity of the air or water matrix, so this is nothing new, just a different view of reality.
Can light travel through "emptiness"? No. It requires some carrying medium, which I've called the matrix.
Maybe we threw out the "ether" theory too soon.

[Aireal]

Jlknapp505

Your basic physics are pretty sound.

Mach's principle can be used to show that there is an upper limit to the speed of light.

Light like all waves need a medium to propagate through.

A dense medium will slow down light.

Thus the speed of light is indeed a variable, not a constant, but does have an upper limit.

So you are correct, this is nothing new, but rather just a different view. But at times a different view on a subject offers new insights.

Yes, the concept of "ether" was tossed out too soon, but seems to be making a comeback among the mainstream.

Glad to hear from you, hope you stick around and explore our different view some more.