[throwaway19342]

There are other approaches you're leaving out. For example, outreach: make sure that you have considered all candidates, make sure that you communicate to them that you truly value them.

We made a couple cross-departmental promotions into the tech team of people who would not have taken the initiative to present themselves as candidates despite having natural aptitudes. In the absence of role models and with the rampant hostility in this industry, good people may take some convincing.

For what it's worth, another cross-departmental recruit matured to be an absolutely incredible engineer, who went from a standing start to making big bucks at Google within 5 years. He happened to be a white guy, haha -- but that's what you get when you cast a wide net.