Let me just jump on the bandwagon and say that this is an awesome addition to Construct. Here's some suggestions that to me would make it an indespencible tool. (I'm sure others have requested the same or similar.)
1) seing a preview of the animation you're making would drastically improve workflow.
2) if possible, a linear timeline type bar for navigating and moving/creating keyframes
3) the ability within the editor to switch any of the bone-animated sprites to a different animation at any keyframe
4) the ability to change the semitransparency and dimensions of an object per keyframe.
as you can tell, number 3 is especially important to me. Anyone who wants to know what I'm hoping to be able to do with bone animation, please go on youtube and check out gameplay footage of "Odin Sphere" for the ps2.