Tom,
Einstein's SR postulates are succinct, specific, were very carefully considered and crafted, and stand above all explanatory descriptions. It's wrong to think we can "suggest" what they are, they are set! Yet I'm often surprised how few really know them, and more importantly what they (in themselves) really mean beyond simply turning a posteriori problems into a priori axioms. I won't paste the original German version, but two close English versions are below, the first including the precurser;
1 (a). Examples of a similar kind, as well as the failed attempts to find a motion of the earth relative to the 'light medium', lead to the supposition, that the concept of absolute rest corresponds to no characteristic properties of the phenomena not just in mechanics, but also in electrodynamics, on the contrary, for all systems of coordinates, for which the equations of mechanics are valid, the same electrodynamic and optical laws are also valid, as has already been proven for the magnitudes of the first order.
1 (b). The laws according to which the states of physical systems change do not depend upon to which of two systems of coordinates, in uniform translatory motion relative to each other, this change of state is referred.
2 (a). [L]ight in empty space always propagates with a determinate velocity c irrespective of the state of motion of the emitting body.
2 (b). Every ray of light moves in the 'resting' system of coordinates with the determinate velocity c, irrespective of whether this ray of light is emitted from a resting or moving body. Such that; velocity = (path of light) / (interval of time)
or more commonly shortened to;
1. "The same laws of electrodynamics and optics will be valid for all frames of reference..." which is to say, the speed of any object is relative to the observer.
2. (a) "Light is always propagated in empty space with a definite velocity c..." Or, as an exception to (1.) above, the speed of light in a vacuum, c, is a universal constant.
(b) "From a composition of two velocities which are less than c, there always results a velocity less than c," i.e. nothing can exceed the speed of light.
The postulates are well proven. But it is a serious error to confuse the efforts at rationalisation and logical explanation, which are NOT proven and which he always knew and said were incomplete, with the proven postulates he stood by. They are sacrosanct. The 'explanations' to date are not. Do you seriously suggest they are?
My point ref 1952 and Minkowski stands. You clearly don't know that last paper. It wasn't until then that he specifically expressed the solution as "small space 's' in motion within larger space 'S'." etc. and particularly of; "not one 'space' but infinitely many 'spaces' in motion relatively" Almost verbatim with Minkowski's 1908 conception, just re-translating one key word; Minkowski's; "endlessly..."
Peter