Just because she is a female version of Cloud. I was disappointed that she didn't meet Cloud in Dissidia. Light has her own story. It would be difficult to fit a timeline in with her, due to the most recent game releases, but I believe she could be a warrior against darkness some how.
I think Hope would be a great role model for Sora, and he would fit in with the other crossover characters nicely :) He has a lot more to his story than I have seen. It would be cool if he learned something by helping Sora in some way.
Or both. Because they communicate very well together. Light is by the book, while Hope is resourceful and creative. Working together, they make a great team!