Hikari was around for nine episodes (ten if you count the very end of the first "Season 2" episode) and...didn't really do much of anything. Satoshi now knows that her Hinoarashi evolved into Magmarashi and Hikari got to meet Iris and Dent, but other than that her appearance seemed really, really forced. I mean, yeah, she was only there to hype up the whole "we're bringing old things back to Isshu now!" thing that B2W2 was promoting so much, but other than that?
We didn't find out how she did in Houen, she didn't catch any new pokemon, none of her existing pokemon evolved, she didn't help anyone else (i.e. she didn't use her experience with her Mammoo to help Iris out with her Kairyuu problem)...she could have skipped out on going to the Isshu region altogether and I don't think any of us would have been able to tell a difference.
So, what do you think the writers could have done with Hikari to make her re-appearance actually mean something? Which of her pokemon would like to have seen evolve? Do you think it would have helped if she had caught something while she was in the Isshu region? What about telling us how her old rivals are doing? Letting us know how she did in Jouto / Houen? Telling us about her Mimiroll's modeling career? Getting a new outfit?