Hypertuned/Resonant

[Singularity]

I think Zenos is a resonant from the first moment you see him.

"But when I read van Baelsar's reports, I immediately saw the boundless potential of the Echo. I saw how it could be instrumental in binding an eikon to one's will. Hence my research and the Resonant - and oh so much more!"
- Zenos

It's made clear through dialogue that Aulus started out as a geneticist - his original proposal was to "modify the Garlean genome" to correct what he sees as the one flaw in the otherwise-superior-in-every-way Garlean race - their inability to wield aether. He was unable to find anyone in Garlemald willing to support his work, until he met Zenos.

Now, why Zenos chose to support Aulus is not 100% clear - either he had read the reports already by the time they met and presumably saw an avenue to achieving his goal of conferring the Echo upon one who was not born with it, or he supported Aulus simply as a path to greater strength and then read the reports later and changed the focus of the research.

Either way, under Zenos, it's clear that specifically the Echo rather than merely the ability to wield aether became the goal of the research. At some point after beginning work, Aulus invents the soul transfusion concept and abandons genetic modification as a path to achieving this goal. His early work lives on however (and possibly continues to progress under a different research team), and while he was not able to genetically confer magical ability, some of his modifications were found to be useful in... other ways, the hypertuned being the result. The magitek implantation may be a later development of the hypertuned or it may be another of Aulus' abandoned research paths. Certainly it's conceivable that magitek implantation would be a potential path to explore with regards to making a Garlean able to wield magic.

Rewatching the cutscene where Fordola wakes up after receiving the resonance treatment, it's clear that Aulus' laboratory is not substantially integrated into the surrounding structure, and it's also not something Gaius would have allowed when he was viceroy (i.e. up 'til the end of 2.0), so it definitely looks like it was constructed in or moved to Ala Mhigo recently.
On the other hand, there are dozens of bodies of presumably failed test subjects placed around the floor, so it seems equally unlikely that all of these are a result of attempted transfusions using the recently-captured Krile.

I would conclude that the laboratory was set up shortly after Zenos became viceroy and has been operating for some time, Krile merely being its newest Echo source. Echo users are not all that rare, and certainly some would have been born in the annexed territories of Ilsabard or Othard, being far more accessible. It's also well noted that the Echo manifests in multiple ways and conceivable both that Aulus would want to collect as complete a set as possible and that Krile's form was not one they had already.

As for Zenos himself, if the lab has been around for some time (and the research itself even longer), then I'd doubt he only becomes a Resonant after capturing Krile. His strength doesn't really appear to change throughout the course of Stormblood (yours simply grows to match his) whereas we would expect a significant jump in power if he suddenly gained Echo-like abilities. The specific way in which he is described as having (effortlessly) slaughtered anyone who tried to fight him during the Doman campaign is also reminiscent of an Echo user.