My feeling is that having a clear leader in place is important, so I'm
also leaning away from the numpy model towards one where
responsibilities are more explicitly assigned.  Exactly how to best make
that assignment is still unclear to me.

+1 for BD(FL) / leader-style from me, too. I like Matthew's suggestion of the top 5 active folks discuss to see which of them are actually interested in taking on that role.

Eric