Seems to be a vacancy. Whos' your favorite choice? Georgiou whose both Emperor and technically a Starfleet captain if a kinda fake one who even might be an android al a The Escape Artist (given she stood up to Controleland pretty well)?. Saru, who holds the highest current rank? Burnham who has held the highest rank in the past? Tilly who was pretty effective pretending to be Captain Killy? Someone else?