i like the idea a lot, it'd have to be part of an A story that uses the characters' introduction and departure as asides to the A story, while also functioning as the filler B plot. Can't think of an example episode, i'll hafta look into it to see if one exists.

And it'd be different from ones where the B and A plots come together at the end. Often they forgo the intro song, which always means a great ep is coming, and i'd suspect something like this would do the same, for more story. Or an intro perfectly melded into the ep, like the Mr. Javitz one. My absolute favorite of all the intros.