What I'd like to see is more "unique" interactions, like Schezo/Ecolo, Rulue/Maguro, Draco/Maguro, Risukuma/Witch, Lemres/Witch, Witch/Feli, Sig/Draco, Suketoudara/Maguro, etc.
Thing is 20th does attempt to be like that at times, with combinations like Witch/Sig, Maguro/Rider or Feli/Ocean Prince and I do like those types of moments, but since there still are attempts at seperating the different eras it ends up feeling a lot more...fundamental and safe then 15th, Arle's story is the most extreme example, but Maguro's story also counts to a degree, since Ringo ends up twice as his opponent, making half of his encounters PP7 charas, which wouldn't even be possible without repeats.
Y'know, the more I think about it the more I realize why I appreciate Sig's 15th story as much as I do, since it covers essentially all bases of what I'd like to see from the series in terms of narrative and Sig in general:
-There's no seperation between eras, Arle,Suketoudara and Rulue make up 3 out of 8 encounters, which is a good balance.
-Amitie isn't even mentioned, instead Onion Pixy, Baldlanders, Ms. Accord, Lemres and Ocean Prince serve as his Fever era opponents.
I should stress that I don't hate or even dislike the Amitie/Sig dynamic, but I appreciate it when she's not stuck on him like a ball and chain, like she tends to be nowadays.
-His bug obsession isn't ignored, but it's also only present in some victory quotes and the ending cutscene. It's there, but it's not his main character trait,allowing him to be more dynamic, once again, good balance.
-We get to see some exploration of the Arle/Sig friendship and Sig's dedication to her as a friend is played in a very sincere way.
-The ecounters with Onion Pixy and Ocean Prince call back to Fever 2. Oh continuity how I love thee.
You get the idea, everything I always ask for it here and accounted for.