Let me preface this by saying I think this is a fantastic tool that, while it takes some time to set up, really helps with making smooth animation in Garry's Mod. This is not a complaint, this is a humble request from someone who uses this tool regularly.

Something that I think would really be a fantastic addition to Stop Motion Helper would be an advanced mode. In this advanced mode, you'd be able to select the individual bones on an entity and animate them separately. Basically you have a separate timeline for each bone.

This, for example, would allow for more fluid walk cycles, since it would allow you to add easing to the arms and legs without killing the flow of the walk cycle.

Just an idea I thought up that would help this tool greatly. Of course, implementing it would be a challenge, so I'm not demanding this be added right away, it would just be really cool to have.

If this is already in there and I just don't know it, or if perhaps there's another tool for just that, feel free to post that in the comments below. :)