luceos This is a nice idea. That would be a lovely hybrid of real time chat and 'forum thread'. I would go for that immediately on our forum as a replacement for our real-time chat plugin.
And it would please some of our users who still bemoan the addition of the chat room (we have 'match threads' for football matches, and also the real-time chat for the same purpose - your idea would perfectly unify them and is really what I've been thinking of for about 3 years, just not as crystal clearly as you have put it).
I do think the future for forums is 'types of threads' (or 'types of discussions'), in a similar way that Wordpress has 'types of posts'. So here, you have a Chat Thread. That dictates the layout and functionality of the thread, as you describe.
You would have Blog Threads; where the opening post is formatted a bit more formally, as a blog article, and the rest are comments.
You could have micro-blog threads, which are more frivolous and could be punched in by having a 'status' box at the top of each forum. No title, just punch in your thoughts. The user gets the option of displaying them in amongst the real threads, or not. To tie that in to how forums traditionally work, if one of these generates lots of replies, a member of site staff or trusted user can give it a title and 'promote' it to 'forum thread' status.
For forum threads, if a thread's opening post is wordy and well-liked, it could be optionally or automatically be granted 'blog thread' status, and if Flarum was integrated with a website, pingg, you have a new blog post (for those more casual visitors) with lots of comments, created completely organically from natural community activity. Not a bad feature for community-driven content sites?
I seriously think you have hit the nail firmly on the head, luceos.