If you can get a 'rationalist' house with roommates from your LW meetup, you can force yourselves to rapidly become friends.

I would advise against this. First become friends, then move to the same house. Some people are insufferable, and you don't want to become their roommate just because one day they decided to visit your meetup and liked it. Not everyone who enjoys visiting your rationalist meetup is a good friend material.

I think it would be good to have a debate about "what do you want to get from LW? / why are you here?" Different people will give different answers. People who gave the same answer now do have something to talk about that is interesting to all of them. Some people want to change the world. Some people just want to chat. Both is a valid goal, but if you mix those people together, it may be frustrating for all of them. ("Why are we just talking and wasting time? Is that the most rational thing to do?" "Why do you always insist on doing something? I have enough work outside of LW. I come here to relax and have an intelligent debate.")

Do something that is not merely sitting and debating, e.g. take a walk together. Or maybe go to a gym.