Something that would be very helpful in the timeline, would be the ability to write a short note or label on the keyframe markers.  For example, you could click on a key frame marker and a text box would appear in the toolbar, (or other place on the timeline).  The animator could leave a note regarding the reason for the keyframe.  Like "Lower Hand",  "Nod Head".  Letting the animator select a color for the keyframe would also be helpful.