Right? Loki's role-less! Cates has done plenty of setup to have Loki pick up a role of some kind and there's just not much left, most roles have been claimed. The Champion role remains pretty much because Thor was refusing to give it up until now.
On the one hand, no role at all means Loki is free of fate, which is good for him, but.... I don't think that would make the best story.