It does need new code. For aggregate threads to work, meetup organizers have to coordinate with whoever is posting them. I don't think that will happen without automation.
It doesn't need to change the site code, and that's dicier than just someone cooking up a bot.
Six out of the last 10 posts are about single meetups. And I care about none of them.
I will look into whipping together some kind of bot that periodically posts threads like the open thread or a meetup thread. Voice your opinion in the comments if you do not want me to do that.
That is all.