Sorry to bump an old post but it does cover my question.
I see it as a common requirement that you'd want a bounding box to be different in size to the sprite. e.g. For pretty much any isometric game where something is "sat" on the floor, you'd want to be able to walk behind it.
Has anything been added to cover this in C2?
Would you consider adding it if not?
I think the best place to put something like this would be the "solid" behavior, new options which allow us to specify the rectangle of the solid area within the sprite (default: whole sprite).