Sheliak got some of his water magic back and he will be eager to show off at the arena, particularly after his frustrating job as a dealer at the casino. Also, as someone who tends to be secretly miserable during social obligations he might sympathize with Azula. He is also going to be doing his own investigation after the kidnapping since he doesn't want the Enma to hold all the information.

Let me know if any of these options sound interesting to you.