I think it would be super helpful to have the additional option of adding a group to an event along with the characters. Thus there would be a column of "Characters associated with this event" as well as a second "Groups associated with this event" column in the "Event/Character" relationship page. There are tons of collective noun groups in ancient Greek myth, and some of them are not groupings of specific people, but generic entities (ie The Athenians) that cannot be back-filled.
For things like the Argonauts, it would be necessary to be able to search for an event using a character in the character filter (like Hercules), and have it bring back events that have him in a group but not listed individually (a bunch of stuff that happens on the Argos).