I can't really understand why people are so eager to open gates of Molly's world to strangers from the White Council. Brass Courts are self-sufficient now, so we don't need external help from WC, before the chance to root out Peabody and other (sleeper) agents among wizards. And if you presume that someone influenced by the Black Council won't try to be in the diplomatic mission or won't try something dangerous in Molly's soul, you are too optimistic.
So, although I don't like it, I am forced to vote for the second plan.
[X] I showed you mine, now you show me yours
-[X] "I allowed your divination, so in the spirit of cooperation and establishing further ties, would you consent to a divination of my own?"
--[X] Assuming he agrees, warn the gathered wizards to expect our anima banner to manifest. "Please excuse the light show. This is somewhat eye-catching, no pun intended." If using the Crown isn't enough to cause the anima to appear, force it to do so as part of the show.
---[X] Using one the Merlin's rings as a focus, ask our Crown to sort the previously established list of White Council traitors by how often they are in his presence. Also take the opportunity to use the Naked Wicked Souls Charm on him.