I'm thinking if we get a legendary event for The Mandalorian it'll be Din Djarin, in full beskar with the jetpack. Every other character in The Mandalorian just doesn't feel epic enough.
Seems like Sackoff's character from s2e3 is also a likely candidate for a marquee, given how much she's already popped up on the Clone Wars and Rebels.
I was happy to hear Moff Gideon is in the works! The empire could use another strong leader to make use of leftover troopers and officers.