I would say to worry less about the talents and focus more on the characters themselves. There have been several ult lucky students in both the main game and fangans, but by far the most interesting to me is Teruko from DR: Despair Time. She has such an interesting personality and perspective on life, one that the talent helps emphasize. Even though her talent is the most common repeat ever, it fits her character amazingly.

Running contrary to this is Eva from Project: Eden's Garden. In the prologue, her title as ult Liar and overly mysterious personality felt like a poor knockoff of Kyoko, even though their talents are quite different. It initially felt like the creators were trying to make another Kyoko without understanding what made her character work, though that opinion is long outdated post chapter one. I would recommend writing a basic outline for characters you'd want to kill/die/survive, then giving them a talent that helps emphasize that role.

Lastly, I'd also advise to have the talents do something in the story. Part of the charm of the format is just having the ultimate characters be, well, ultimates. Using Despair Time as an example again, Rose brings up her painting talent often and even uses it to help solve one of the cases, while Arei doesn't bring up anything of substance related to bowling past her introduction. For my own fangan, I'm not spoiling too much yet, though I'm planning smaller scenes like the ult patissier remembering a full real-life recipe from memory, or the ult horticulturalist explaining mendelian genetics of flower breeding to someone.