I feel there is much confusion regarding Ezelcant "Darwinist" agenda. Probably has to do with the use of the term "Superior" in show, which get assimilated with stronger. In effect, instead of the
Ubermensch, hig goal is more the
Last Man.
In previous Gundam shows, Newtypes and the likes were often classified as the step toward the Ubermensch, now remember that in contrast to that, Ezelcant has repeatedly labelled them as a regression.
Thus, rather than a darwinist approach, I'd tend to see him as vying for a form of posthumanism. Hig goal being to create a race of human wise enough to live in harmony.
In effect he isn't selecting violent humans and X-rounder, but drawing them out to die on the battlefront, ala Treize (also reminds me of Lelouch BTW), with the not smart enough dying in colony destructions, only leaving those apt enough to survive adversity in non violent ways.
IE, he is aiming for an "understanding" ending, but by weeding out those unable to understand each other.