Definitely need—at a minimum—Chirrut, Baze, K-2SO, Bodhi and Krennic.
Ideally though, U-Wing (I'm totally reading into that wink, Darth Anton), Scarif rebels, Saw Gerrera and his militia, Rebel pilots, Jedha citizens, background characters from the Ring of Kafrene. Mon Mothma would be such a welcome resculpt, and a new Grand Moff Tarkin as well.
It would also be a good opportunity to get a new Y-Wing.