Let me play Halsey's advocate here for a second... Which is unsurprising similar to the role I play in real life.
She, like a majority of scientists would never even consider this aspect of "playing god".
Statistically speaking, those who study science and are active in their various fields pay very little attention to the qualms of those who believe in supernatural beings.
This goes double for someone like Halsey who I suspect feels the idea of such preordained moral rules to be utterly without merit and probably something to be challenged at every step.
In the case of what was revealed about the Forerunners in their trilogy, it seems their entire existence was one of advancement of their own species through genetics, they lived astronomically long lives because of their knowledge and abilities.
This is something I believe the good Doctor believes to be a worthy goal.
There was a 343 vidoc after the release describing the story process and their pillars for creating the narrative.
From what I can remember they used Halsey as their icon for the 'hope for Humanity' pillar.
Personally, being a scientist myself(plasma physics), I do run with the logic that bettering ourselves through genetics is the next step.
Obviously not for the reasons some would ascribe to the idea of genetic modification, but more for the ability to create healthier kids and weed out the defects that gene's inherently have.
I could get into a huge section on how the advent of global travel has inadvertently stopped the usual evolutionary isolationism process that most species go through, but that subject is best explored in ones free time and probably not on a Halo forum
And yeah, I basically gave up on Halo 4's multiplayer a few months ago... I feel like perhaps it's too much a departure from the old days.