Ideally, the PM area should behave like a 'private' topic, I'd say...
We can have these now, with topic privacy. i.e. you start a topic, set it to Contacts, and only your contacts will be able to see it. Once I get around to finishing my buddy rewrite, you'll be able to put people into various groups, so you can choose to have topics only for your family, only for your friends, etc... (I don't know how I'm going to handle that yet, though... Ah ah.)
But, err... I lost my way. What I meant is, we should have only the 'convo' view available, and show messages using the same code, i.e. the Display template... Or maybe, just ditch the PM system and instead create a special board which will get the private topics, but then you risk losing access to a topic if you're suddenly removed from the contact list, hmm........ :-/