Eckard
Very nice essay. Nicely written and I also agree with most therein, certainly including Darwin. I've just speed read most for now but I'll read again slower and make notes.
I also agree your response to JOHN ref the SHAPIRO effect. Venus express found more than enough gas atmosphere for the delays found. Shame such clear refutations don't spread.
But I still see flaws in your simple sounding 'c';
1st; Who can properly determine 'Time of Flight'? The answer is nobody! Choose an observer and I'll show you his problem.
2nd; Take a scenario with an emitter near Mars heading for Earth, which is heading towards it, then an intermediate probe in Earth's ionosphere (sending 'check' signals to Earth & back). We know the signal travels at c wrt the sol rest frame. It's recorded by the probe on passing it, then again on Earth. Your description will fail because either it does the last bit from the probe to Earth at a DIFFERENT SPEED to the probes signals, OR it changes speed on passing the probe so falsifying your description.
Of course it does the latter (as at Venus) but also then does c in the LOCAL rest frame. (as ALL physics is local). It therefore does TWO speed changes on interaction with fermions & gas, to the refractive index PLUS to the rest frame of the fermions it's been re-emitted by. You should find that matches all observation flawlessly. Remember fermions live in all space.
Of course SR is wrong, but you really need to impartially review your alternative as we'll need a flawless one if it's to stand any chance of replacing SR!
Peter