To start, I categorize a "Character Piece" as a mission where in a non player/crew character is heavily involved with the storytelling in a mission. It can be done many ways, but at its core is the inclusion of one or more characters who's identity, personality, or actions greatly influence the mission if aren't actually the point of the mission/story as a whole.
There were many episodes of the Trek series that I would categorize as this, some of them being the best or most thought provoking episodes of their perspective series. "Inner Light", "Ethics", heck... "Where No Man Has Gone Before" even.
Now the reason I bring this up is I find myself at a personal quandary. I like character pieces, but, when making missions for an MMO I want to stray away from them. Mainly because the most important character is the player, everything else should be supporting cast. You can still do them well keeping that in mind, but, it is a dangerous threshold to Suedom and one I'd rather not flirt with.
All that said; two of my three published missions are character pieces. (3 of 4 if you count the one I made for my fleet and don't advertise.) My duel perspectives project I am finishing up now comes dangerously close to being called one because of the respective titular characters and their importance to implying each factions perspectives. Any more missions of mine that include Amanda Barclay with anything other than a passing glance will be stolen by her, I know it. She's just too fun to write. And most of my list of "next projects I want to do" (A revisit to the Galactic Barrier/A non-combat Diplo mission involving Trill Symbote ethics/Story of an Aging Klingon hunting for a good death) get most of their importance from one or more very important and unique character.
The one mission type I don't want to use and I come up with my best stories with it. : /
I guess I am asking, what are your thoughts on missions I call "Character Pieces"? As authors, as players, as Trek fans, MMO enthusiasts.