A druid PVP healing CC would be cool. But it is probably too hard to make any "good" one, since it cant really stop-cast, its more like a constant moving type healer. Form switching and the like.
I might try and make a CC with a behavior tree just for that.
PS: back in October when I was hanging out with apoc and the like, the idea of a behavior tree came out and an article was presented, I quickly coded up something as a "notes" type thing. I didnt use it, but the idea got stuck in the code, maybe you can find some use for this. Its in the attachment. It isnt finished, and it isnt the best implementation possible, also, it was beeing built with WoWRobot in mind, not HB, but it still gives a good idea of how it works.