First, no one has databases which let you select even a few variants. We know a bunch of mutations which reliably decrease intelligence. I don't think we know what reliably increases it.
I am aware of this. But you were the one discussing the hypothetical that the Chinese government would be more likely to do an embryo selection program aimed at modest national-wide increases in averages; clearly you are presupposing that such databases exist, and so I'm not sure why you're objecting that your hypothetical is currently a hypothetical.
Second, the idea that we can just pile all the small improvements together to get a supergenius relies on unlikely assumptions, for example the additivity of these improvements
My understanding is that, far from being an 'unlikely assumption', methods like twin studies & GCTA used to estimate aspects of the genetic contribution to intelligence have long shown that the majority (usually something like ~70%, going off Meng's citations) is in fact additive.
and lack of negative side-effects.
High IQ types don't have that many problems.
hypothetical that the Chinese government would be more likely to do an embryo selection program aimed at modest national-wide increases in averages
I probably wasn't clear. The hypothetical program would not be aimed at modest nation-wide increases. It would be aimed at figuring out how to genetically engineer intelligence. I expect that its first fruits would be modest increases in the averages of the program subjects -- not the averages of the whole population of China.
...the majority (usually something like ~70%, going off Meng's citations) is in fact
I suggested recently that part of the problem with with LW was a lock of discussion posts which was caused by people not thinking of much to post about.
When I ask myself "what might be a good topic for a post?", my mind goes blank, but surely not everything that's worth saying that's related to rationality has been said.
So, is there something at the back of your mind which might be interesting? A topic which got some discussion in an open thread that could be worth pursuing?
If you've found anything which helps you generate useable ideas, please comment about it-- or possibly write a post on the subject.