It's an interesting theory, but it's hard to rectify with some of the stuff these same powers do (e.g., take a known +100 IQ cohort and bring ~80 IQ mongrels into their towns, and then encourage them to mix). In order to get from there to the evolutionarily path you're describing, there is an inordinate effort required, compared to some more obvious vectors.
It's an interesting theory, but it's hard to rectify with some of the stuff these same powers do (e.g., take a known +100 IQ cohort and bring ~80 IQ mongrels into their towns, and then encourage them to mix). In order to get from there to the evolutionarily path you're describing, there is an inordinate effort required, compared to some more obvious vectors.