I didn't bother reading the OP, nor am I familiar with Aubrey's proposed solution, but imo the obvious remedy is simply instituting a stipulation: life or kids. Big fucking deal. It's an easy choice.
It depends on how this affects the population composition of humanity in the future. If the smartest and least superstitious individuals choose life, and the lower intellects continue to reproduce vigorously, over time as the best died due to accidents, their rate of replacement may not be sufficient, the lower intellect masses could grow to become a larger % of the population.
My take is that reproduction is a privilege not a right. Society can take the natural way away from the masses and bestow an artificial method with certain limits imposed.
IF intelligence is found to be something that can be increased without bounds, it is likely to require vast resources as it is increased. Conceivably a constantly enhanced individual might over time take more and more resources, eventually exceeding that of millions or billions of unenhanced individuals. I do not think this should be prohibited, nor does it seem likely that the policies of a group of such could be obstructed or denied by those with lesser enhancements.