Assuming React(Composite)Component continues to manage _pendingProps and _pendingState, I think this can only work if ReactUpdates is aware of where the parent/child relationships lie or else it's not possible to easily determine when an update can be skipped due to a parent having been rerendered.

I'm actually unsure of how to find parent/child relationships when given a few ReactComponents -- ReactInstanceHandles doesn't help since there might not be separate DOM nodes.

Let me know if that comment made sense, not 100% sure I understand what I just wrote.