Bleu was only zoned last year so if you had passes for the same zone you should have been ok? Allocated pitches should help with late arrivals as long as you book in one go.
Anyway, I think you may struggle on BSJ trying to keep space for latecomers, I understand that lasy year the site was filled from the front so day 1 people were just inside the gate and each section was filled before the next opened.
I would make sure the first arrivals hold ALL of the camping passes to make sure you get the space.