IMNSHO: Each person should carry a picket -- and stashed in a way so if you're holding a fall, you can whip out the picket one-handed, and place it, whilst still keeping t' other hand on your ice axe anchor. Practice a bit beforehand.
Bit of a drag if the persons carrying the pickets are the ones in the hole.
Of course, the later in the season, the harder the snow and the less the likelihood of getting a picket in solidly one-handed.