I was thinking maybe 3 bones... one for the thumb, one for the first two fingers, and one for the second two fingers, with them then parented to their group.

You;d have to build grasp and thumb grasp with erc since its non standard old styled poser rigging, but I think it'd work.

You would need twist or rotate either, just bend... and could build erc to bend the hand properly, and the fingers would follow.

Way too many people take way too many things way too seriously.