[In response to the discussion in comments to Solution 1:]
Where should you try to seek an advice on this topic? I explained, probably not at this Quick
Questions & Answers forum. If not here, where else?
How to explain it..? It all looks a bit weird.
Imagine A. Einstein writing to the general physics discussion forum (including people working in thermodynamics, electricity, mechanics, etc., and, as always, most people working more at applications or experimental techniques): "I am working at a new theory of mechanics which, in particular, should reconcile recent negative results on ether discovery, but it will need to radically review the present views on time-space. How could I modify the Galilean transformation in a proper way? My idea is to give up the independence of the masses and sizes of the bodies on the reference frames...".
If such question was asked at that time, most members would locate a red flag for abuse reporting (on this page, it's above, below the question), click it and choose to report "Not clear or incomplete".
Now, think about one more thing. Imaging someone (Henri Poincaré, most likely, if any at all), would provide a comprehensive advice to A. Einstein. Who do you think would now be considered as the author of the Special Theory of Relativity now?
This example is a bit of exaggeration, but are you getting the idea?