Here's a few possibilities/theories I have formed so far, in random order:
Ken as destroyer, the voice of Shiva. Ken has steered Noemi to become somewhat of a destroyer, as it was referenced the 'voices' were always there (I believe it was said even before Noemi's birth). The Shivans may have an agenda of any kind, perhaps being pessimistic about the Terran potential as future Brahmas and wanting to exterminate them pronto, to open the road to other yet undisclosed or undeveloped races. Alternately, they might be trying to ruin the plans of the Vishans: perhaps a direct result of Shivans and Vishans having lost their apparant mutualistic purpose (their broken triad).
Ken as preserver, the voice of Vishnu. Ken has steered Noemi to 'do what has to be done'. It's all a matter of where one draws a very thin line of when one is destroying to preserve and destroying outright. Getting rid of the GTVA or forcing them to give up their war and thus being the subject of many changes and public outcry may help to make the Ubuntu a wide-spread way of life amongst all Terrans, also beyond Sol.
Ken as the legacy of the Brahma. Ken seems to teach Noemi the responsability to destroye AND preserve: by destroying one being the other thrives. Noemi has spiritual background of Ubuntu, which may serve to be able to judge who lives and who dies. While this can be seen as but one persons perspective and sound hypocritical, it's never said if the Brahmas were unbiased or not. If the Brahmas are builders, creators, keep in mind everything and anything can be created in an infinite amount of ways, some (if not all) neither right nor wrong.
Ken as a red herring. Ken may just be a by-product of scizophrenia and not be a direct voice of any kind at all. Noemi being scizophrenic may simply be a means to ensure she can do what she does today, although given there's some hints by Bei at the end of WiH1 that someone can listen to a great power I'm not sure if a red herring is in place here.
But frankly I don't know what happens in the end. Maybe all Terrans die and Kohnsu, through learning and observing from the terrans leads his people into a direction the devided terrans never could. And whatever role Ken plays can be many outcomes.