Children's Crusade gives a sort of idea of what the original plan was supposed to be before the second "season" of Young Avengers got delayed: Nate would leave to become Kang, Cassie would start to get closer to Kid Vision, and then Nate would come back in time (having been tricked into thinking Billy's life depended on it, as we saw in the Children's Crusade one-shot) and get into a triangle with Cassie and Vision, paralleling the Scarlet Witch/Vision/Wonder Man triangle.
All of this is there in Children's Crusade, but rushed. Some of the ideas for second and maybe even third series of Young Avengers got done while Heinberg/Cheung were on hiatus (like the "Young Masters of Evil" concept that got done during Dark Reign) but not in a full-fledged way because they were trying to save the property for Heinberg/Cheung's return.