I thought of that, but... still! Hydra could've helped themselves to Bucky's relatives, who'd have similar genes; some nobody middle-class New Yorker vanishing wouldn't be hard to pull off for an organisation like that! Or - going back to the "biotech in this universe is far more advanced" thing - they could try cloning, which seems a really obvious approach to me as a science-type! (Broad hypotheses are narrowed down gradually. Zola was disappointed that only one test subject survived the process, so the next logical step would be to see whether that was a fluke, or a specific quality of that subject.)

...I may have basically prompted that on a kinkmeme, once upon a time. :D