Hmm, what you are suggesting in the beginning sounds just like Quassel:

It is a Bouncer with full PostgreSQL database of the whole log, full search functionality, a shared history between users of the same bouncer, etc.

There are clients as a website (runs on node.js), for Windows, Mac, Linux, iOS and Android.

So, if someone would add the missing features to Quassel, we could make that one the new new HipChat.