As a work around, could you run some code after the first is completed, and delete the first task then recreate it "completed". Would that not then reorder them? Since it's a completed objective would it matter to the players it had moved in the ingame map?
I thought at first the new briefing was a complete PITA, but the more I play with it the more I'm enamoured by it, it makes dynamic briefings so much more neat and achievable.