That's exactly the problem, though. There are so many extensions that it's about as much work finding out which ones are even needed and how they interact for y

That's exactly the problem, though. There are so many extensions that it's about as much work finding out which ones are even needed and how they interact for your case (in this case the replay) as is implementing, say, a good chunk of IRC. And no, I'm not exaggerating, I've done both and decided that writing XMPP clients is not for me a long time ago. Addendum: I really love XMPP, but I do think the many many extensions have hurt it more than one defined spec. And yes, I know it supports many use cases, but I simply only care for 1:1 and multi user chat.