Hey Jake, Colin here, great plugin!
I had made a version of exactly this plugin but it broke with 3.1 and I hadn't quite worked out the bugs anyway....
Just a comment about inter-child-parent dragging, my version was based on the nav menu method of giving you an outline of where you were dropping it, so that you could move left or right to know which family or generation you were aiming for. For me I'm mostly using this for simple repeating custom post types so I don't miss the generations thing, but it's a possibility for a future release, it seems to be one of the most popular comments.
Keep up the good work!