I think something that could liven up bitcointalk is a chat feature, it could be like a live chat where you can continuously talk with others. Think of it like a chatroom/trollbox where you could chat with many other people at once or even one on one. If there was chat I think this would make even more people stay on bitcointalk and take part in the discussion.
I've seen this particular feature on another SMF forum (altcoins talks to be precise). Well although it's a nice and fun feature It's not something that's utterly important and it may end up being buggy because of the traffic volume of this forum. If it's something you intend to create as probably an extension some people may eventually use them
Aside that, if you intend making something like a patch for the forum I don't think the admin would be accepting it besides, I don't think I would even support the motion of making that level of modification to the forum.