cust, TL;DR: No.
In a theoretical way is everything possible, but no. I have no intent of replacing website. Even maintaining existing features is pretty time-consuming (because I'm doing dirty-parsing of Facebook html pages), so every Facebook change must be incorporated in plugin (and such changes are very often). Doing this with posts, comments, etc. would lead to much much much more of these problems and spent time.
Even if I would be willing to parsing these things etc., it would need much work in creating user interface for it, because your example isn't possible - posts couldn't be incorporated into Miranda's message windows (only if every post have been single contact, which is madness and nonsense). So it's just too much work. And worthless - just use website, everything works best there :-)
