Considering the other mentions of a legit use case for continuing the group, and the problem of a random "new owner" swooping in and sniping the group/list for their purposes, I wonder if the solution is to intentionally corrupt the list [0]?

At least that would prevent the sniping. In your case, do you have any continued access or has control already been sniped?

[0] Delete all but a few members, replace all members's email addresses with junk/temp email addresses, etc.