Klingon songs and opera would make a great addition to the game. (I wonder if they could add 'U' to the game's soundtrack?) As burned out as I am with lower levels on both sides of the fence right now I would gladly make a Klingon character (My mains are a Joined Trill and a Gorn) and grind him to cap if I could make him sing.
Even if emotes are out of the question imagine the potential for an in game concert of some type. You could have a 'diplomatic event' in game and have captains from both sides attending to listen to Klingon Opera and songs, as well as some Earth music. (probably something in public domain like Bach, or if you could swing it, Wagner, The Planets, Russian Choral groups, etc. something with a Klingon feel to it) You could make it part of the Captain's Table, or, for added craziness, you could have it be a cross faction mission where the concert gets attacks halfway through, say by the Undine, and both sides fight their way out together.