Could you explain why you want to drastically alter Vista's characterization, since she's not shown indications of sharing your zeal for transhumanism prior to this vote?
Sure!
Its not altering her characterization as i see it.
Vista is basically a child soldier. Shes been fighting for years, i think by this point longer than some
tours of service. But the organization she works for, while putting her in that situation, also insists on treating her like a normal child. The disconnect causes her issues in canon, and here. She yearns for respect, to be recognized for her accomplishments, skill and experience. Thats canon, and its true here.
The fact of the matter is that Vista sees her age as the problem. If she could flip a switch and be 18 shed do it in a heartbeat, without a second thought, even though doing so would objectively cost her like five years of her
life. Thats a not insignificant loss of time. But its a price Vista would pay gladly for the respect she feels her due. But alas, no such switch exists, Vista has no way to climb that ladder except by waiting to actually turn 18.
But now she has a new option. Now she can
make herself better. She can do it
now.
Because ultimately? Age is a function of her body, of her flesh. And now she has a option to replace it with something
better. Stronger. Others may disagree, but she will draw
strength from that rejection for it no different than how t they treat her already. She can embrace potential, become more than she is, more than her body allows her to be.
So what it boils down to is the fact that Vista never showed any interest before because she as never cognizant of it being a
option before, and now that shes twigged into the possibility, it provides a ready solution to all her issues (or atleased, what she sees as her issues), while making her a
better hero.
(As a aside, this path also brings her closer to Taylor and through her the TSAB. Who will literally give her everything shes ever wanted. Respect, recognition.
They wont treat her like a little girl, but the veteran she is. I wouldnt be surprised if she tries to jump ship the first time she runs into a girl her age as a squad leader or something.)