From my comment:
Groups, I'm actively against supporting here. But there's something I think we could do to help make groups work, that's more of a general solution: adding the view object itself to custom_list, so each entry would look like (path, name, view).
This would let people pass data into the template by attaching it to the view, like:
def my_admin_view(request):
return render(request, 'my_admin_template.html')
my_admin_view.group = 'group 1'
admin.site.register_view('my-admin-view', view=my_admin_view)
Then they can override the template to group however/wherever they want.
From my comment: