Waititi voiced this character in the Mandalorian so it makes perfect sense for him to show up again in a film directed by him.
IG-11 was a merciless bounty hunter who formed an uneasy alliance with Mando in the premiere episode of The Mandalorian.
SPOILERS if anyone hasn’t watched The Mandalorian yet, but IG-11 is shot by Mando when he’s about to terminate Baby Yoda. He then is repurposed by Kuill and becomes a sort of nanny to Baby Yoda, ultimately sacrificing himself to save the group and allow them to escape from the clutches of Moff Gideon. Despite being a droid with no human emotion Waititi was able to bring plenty of humanistic traits to this character and really flesh him out.
IF IG-11 appears in a Waititi directed film, it would have to be set prior to the events in The Mandalorian. No matter what the plot of the film is, it would be fairly easy to incorporate a bounty hunter like IG-11 into the story. Fans would love to see this extremely serious and dangerous assassin droid on the screen again, and perhaps a reason can be given as to why he’s so willing and almost eager to self destruct.