One short-term solution I can see helping with this problem is to have rationalists cluster closer together. This already happens indirectly, when geographic locations are occupied by organizations and cultures that attract or require people with a higher-than-average rate of rationalism. We could encourage this on different scales, clustering in cities, regions, or even in neighborhoods and houses. My housemates and I are already doing this. We collect the more interesting, motivated, insightful people we meet, mostly from the university, and integrate them into our social network. Occasionally we invite them to move in with us. On a slightly longer timescale (2 months - 2 years), we have been discussing moving into a larger house with more people. It is a slow process, but we are seeing progress.
We have managed to collect a group of 4-5 around classes and hectic life events in just under two years. While this is still too small a number to draw any firm conclusions, the rate of acquisition seems to be increasing, and I strongly suspect it will further accelerate the more people we have.