The original meaning of 'Shemah Yisrael'?

The various meforshim have long puzzled over the meaning of the iconic phrase 'Shema Yisrael, Hashem Elokeynu, Hashem Echad'. Most people translate it simply as follows:

'Hear Oh Israel, the Lord is (our) God, the Lord is one'

i.e. As the quintessential proclamation that there is one God, and Hashem is Him. The problem is that the hebrew is a little awkward. Some people like to translate 'Echad' as 'A unity', which is a bit more Rambam like.

I recently read another theory which sounds truer, and also fits better with the Asseres Hadibros. According to this theory, Shemah is really saying the following:

'Hear oh Israel, Hashem is OUR God (as opposed to the other Gods in the pantheon who are not OUR Gods), Hashem Alone (is our God, and none of the other Gods).

Similarly, the first of the ten commandments reads as follows:

'I am the Lord your God, who brought you out of the land of Egypt, out of the house of slavery; You shall have no other gods before me.'

Which really means to say:

'I am the Lord YOUR God (and none of the other Gods are YOUR God), and I brought you out of Egypt and Slavery (and that's why I'm YOUR God because of what I did for you) and that's why you shouldn't be worshipping any of those other Gods.'

All very clearly Henotheistic.

But, if you really want to kvetch, you could possibly say that this is like korbanos. Bnei Yisrael were not ready for Monotheism, nobody was back then, so the only way Hashem could make it work was to first make Judaism appear to be Henotheistc, and overtime wean the Bnai Yisrael away from Polytheism, via Henotheism to straight up Monotheism. And Monotheism itself had to evolve from an anthropomorphic Monotheism where God had a body, to the abstract Deity of the Rambam.

You could also take this one step further, and say that Hashem's ultimate plan is for man to realize that an abstract Deity also isn't a real or true concept, and that eventually we should all become ignostic. I actually believe that theory.