A concept for a new playable-race, with lore and feasability considerations

[Enkidoh]

Yeah, it's mentioned repeatedly throughout the game's entire storyline from even 1.0 that the Echo is transcending the boundaries of the soul, both the user's own and the souls of others. This manifests in various ways, but specifically viewing another person's memories as if they themselves had lived them, understanding another language without actually having learned it, being immune to tempering by a Primal, and much more.

As this information is spread out throughout the game's story it would take me forever to track down the screenshots I took which I could quote from specifically, but I can steer you in the right direction - the very first meeting you have with Minfilia when you first joined the Scions she explained this specifically. So yeah, as Kaiser stated, it's made very clear the Echo is soul powered, and because the soul (as in, life itself) comes from Hydaelyn, the Echo can only be gifted to someone born from Hydaelyn - an artificial construct like an automaton simply would not have access to that, no matter how much you try to handwave it away.

[WellFooled]

I can steer you in the right direction - the very first meeting you have with Minfilia

There's the reference I was looking for. I looked up that cutscenes, her exact words are

Yours is the power to transcend the boundaries of the soul--a power known as the echo. The echo allows you to pass through the walls of a man's soul, and hear the resonations of his past. You will be in his memories, and see things as he saw them. You may even interact with that which you see, though you cannot change the outcome of events. For another blessing, the Echo will enable you to know a man's mind even if you cannot comprehend his words.

Now that I have this quote though, I want to play devil's advocate. It describes the echo as transcending the boundaries of the soul, but the context of that statement only ever speaks of other people's soul, not the echo user's. Nothing, at least from this quote, expressly says it does anything to our soul or even requires that we have one. It's a logical assumption, but not expressly laid out.

Also, does all life come from Hydaelyn? The Ascians appear to be alive, but (unless they were from Hydaelyn to begin with and were turned) their origin looks like it's from some other source. I also thought I read somewhere that Midgardsormr is not of Hydaelyn? So if Hydaelyn is only a source of life and not the source, can she only give the echo to life she is the origin of? How do we know this?