I think it would be interesting if they brought Maddie back with just her memories before meeting Scott or Alex, that Maddie was a pilot with a personality of her own, she would have oportunity to become someone else besides Sinisterīs pawn or Jeanīs clone or Scott and Alex lover and it would be a nice way to give her arc new life. They could even bring her without powers, so there would not be problem with her living on Krakoa alongside Jean.
For some reason marvel always has been way too cruel with clones, another I would like to see again is Joseph pre- Magneto not a hero, a magneto looking person who thinks they should embrace humanity again would be fun to see, especially since Magneto did recognize him as his own person.