AIs != CFD.
Well, the personalities come from AIs. Mostly.

That much is clear from the fluff I've actually bothered to read.
It is written onto the nanites in fragments and then scattered, and with some luck enough of it comes together in a host to form that personally again, thereby overwriting the old one.
It is also to assume that the realities of the wetware impart something on the developing personality, with some memories being kept and skills taken over, and the general view of life of the victim while being taken over partially forming the "infancy" of said personality.
Given the stark unbelievability of the whole concept, I'm loath to actually do anything that direction, as so far that particular avenue of killing the suspension of disbelief has been kept out of games I was in, but I'm good at theory crafting.
@fseperent You ninja! Well, I didn't really think about those implications. Now that I do, it's clear it wasn't meant to be, given that the AI picks up a lot of skills completely useless to a metahuman, but nothing in the way of physical skills, unless it was a drone combatsoft. Still, the idea is nice.