Purposes are tools humans use to give their own lives meaning, if they desire. Purposes should serve humans, not the other way around.
I wouldn't be that into assassination as a vocation even if I had superpowers that made me an extremely good assassin, for example.
Obligatory: https://en.wikipedia.org/wiki/Brave_New_World
What if you sequence the great computer scientists and average ones and find some genes that really make a difference? What if you sequence sociopaths and discover a series of genes that correlate heavily with it? Sexuality, flight or flight responses, physical aptitude, mental aptitude.
We've spent millennia doing a less advanced form of this on dogs, can you honestly say a lot of these dogs we've bred for specific jobs aren't "into them"?
No, this entirely different to that. I'm saying that a person's physical attributes are orthogonal to that person's personality. I'm not discussing if their personality is a result of nature or nuture, just the fact that if you're, for example, physically predisposed to, say, being able to grow large muscles, that has no bearing whatsoever on whether or not you are personally interested in, say, competitive weightlifting (regardless of whether or not that personal interest (or lack thereof) is a result of nature or nuture).
The fact that you are predisposed to be able to grow large muscles is obviously nature; the circumstances surrounding whether or not you actually do grow large muscles is open to the nature/nurture debate, as well as the psychological manifestations that might lead one to engage in (or avoid) bodybuilding, competition, et c.
But the problem is parents would be making that decision. Or in this case a dictator's military haha.
There are already hover parents living vicariously through sports, music, chess whatever.
I can imagine this going to extremes with parents making these forever physical decisions.
Elite athletes can chose to endanger their health for the sport they love.
But I'm not sure about the ethics of a parent deciding to say give lower resting heart rates/higher vo2 max with cycling in mind, even though it could be deadly slow.