You may be able to insert the new entity in the correct order by reordering the list after adding it by resetting the other children's order using the EntityParent command.
If EntityParent does move the entity to end of the child list (pretty sure it would) the list after you add the new version of child 3 would be 12453 so calling entityparent twice on the third child may be able to reorder the list, (first call should reorder to 12534 then next call will reorder to 12345).
If EntityParent does move the entity to end of the child list (pretty sure it would) the list after you add the new version of child 3 would be 12453 so calling entityparent twice on the third child may be able to reorder the list, (first call should reorder to 12534 then next call will reorder to 12345).