I don’t know if the “Every captain needs a mate” is the official tagline or if it’s just something the OFMD Twitter account threw in there when they posted the poster with the air date. But I have Thoughts.
Izzy leaving Ed will make him spiral even more, because he hasn’t got his First Mate around anymore.
Stede needs to team up with Izzy to truly become a pirate captain.
Co-captains need a First Mate too, and they could share one.