Cool stuff. Over the years I notice my IQ peaks about 10:30AM at 146. During non-peak times it runs about 137. So I started making important decisions at peak. This has helped in both work and my private life.
There are super high IQ people in history that didn't appear to affect the world to any extent. So I think the premise that IQ is a factor in a person affecting the world is reaching to something that is just not there. It is probably a choice in how the individual interacts with society and what choices they decide to make.
I can see that someone who is creative, with a high IQ could see many possible paths/solutions from a certain vantage point, where someone with a lower IQ and not very creative would see fewer paths/solutions.
Even faced with limited solutions there is still the choice of the virtue/moral solutions, and some individuals navigate the problem well with low IQ. So I'm pretty much with you that there would need to be significant data/evidence before subtracting autonomy from an individual with low IQ. (of course I wouldn't invest authority into a institution that could subtract autonomy from anyone anyhow ;) )