2) A bulk Direct-Add ability. Rather than checking hundreds of boxesNever mind.
It turns out I can do this with Direct Add on the primary group. I get an error for each member who's already in the primary group, but they do get added to the subgroup checkmarked on the Direct Add page.
And as a bonus, from my point of view, they don't get the "You've been added", presumably because of the error on the primary group add.
But I as moderator still get the notification:
"New Subscriber To firstname.lastname@example.org"