Tom,
I'd describe E=mc^2 as a 'consequence', but we mustn't get into semantics. I point out that of what most consider 'the theory' is actually just 'explanation'.
Thanks for the lectures link, a nice refresher as it's over 20 years since I read those. I'm sure I've mentioned; I've studied Einstein's work for around twice that long. Like others who've done so I give most credence to his later work, which is very lucid, coherent and is much developed from that of 30 years earlier, which he well recognised. Would you like others to believe you own work of 30 years ago in preference to your views now? I'd doubt that of anybody.
So I agree the foundations and axioms of my proposals differ subtly from most in that they're a faithful continuance of Einstein's thoughts, right or wrong. In an axiomatic theory the axioms should be accepted and tested in terms of self consistency and correspondence with observation. If you can't do that, and revert to the explanations from 30 years before instead, then I'd have to point out you're not doing science but beliefs.
The most key and latest paper was his extensive 1952 (English Trans. 1954) comprehensive re-visit and rationale; under the unassuming title "Relativity ...", Notes to the Fifteenth Edition." Many who'd gone charging off building and lecturing on their own interpretations didn't actually like this paper much because it challenged some beliefs even then. You'll find it noted as; 'still under copyright' so difficult to find (a free link to)! But he was quite unequivocal. As everyone else uses his older stuff do you really think it unreasonable that someone at least tests his later conceptions and explanations? (without of course trying to 'judge' them against the previous ones!). I'm sure you don't.
So I've built an ontology to test based on his latest work. This includes the comment, very pointed because he recognised the issues with the interpretations that even he couldn't resolve; "The Special Theory of Relativity theory is entirely contained within the Postulates." What he was saying was that all else is validly open to question. This reflected the fact that none of the many 'proofs' of SR were of the 'interpretations', ALL were of the postulated effects. He then specified the conceptual relationships and aims which any completion of the theory would need to meet.
These centred of course on his beloved 'Local Reality', and implicitly unification with the quanta. He knew his theory always lacked some real underlying 'mechanism', and had stated in the 1940's he "hoped someone one day someone would find that better way" to derive his postulates. I'm suggesting that 'other way' is equivalent to conceiving a car when only horses have ever existed. As Feynman predicted the truth will of course "at first look wrong." I'm not saying the DFM is the truth, just that if it is it will of course first look wrong!
Now if you're prepared to fairly help assess and falsify a possible mechanism to drive it on that basis, then I can explain it very simply. Only then can you fairly judge and falsify it. If still not, then just let me know.
Best wishes