It's long and probably unrealistic, but no one said I couldn't dream...
Things I want:
Memory Link: It was one of my favorite things about BW2, tying the games just a bit closer together.
Vs Seeker/Rematch: Self explanatory. Let me re-battle those who I soundly trounced earlier.
Trainer Customization: I take great pride in making my sprite look great and then showing it off in online battles and trades. Let me show off. But you need to give the guys more options. Actually give us all more options but give the guys equal to the ladies. (And give me back my super long ponytail from X/Y)
PSS: I do not like having to go to the plaza to get to online features.
Post Story: Alola is such a fun region, give us things to do after like Battle Frontier and such.
Ribbon Activities: I love ribbons. While they are mostly a cosmetic item, it is something that I love doing for my favorites, sprucing them up a bit and basically showing off how they are my favorites.
Apricorn Balls: Look, I don't care if you need to make Kurt's brother live here. But only one of these pretty things per file is absurd. Not to mention frustrating.
More Alola Forms: There are no words to describe how excited I was when these were revealed. The idea of pokemon adapting as completely different types is so exciting for me. The fact that it's currently limited to Kanto-Only is not as exciting.
More Mega Evolution: I'm not saying EVERYONE gets a stone, but give newer pokemon a chance too.
Free Fishing: Being locked into fishing spots is stupid and frustrating.
PokeRide: Taking out HMs was something I love and support 110%.
Things I Possibly Want With Some Changes:
Safari Zone: I like Safari Zones. I liked the concept of the Friend Safari. I did not like that by attaching it to our system's FC, we were locked into what was possibly a garbage safari that no one needed and that it locked up over half of our system's friends list to get all the ones we wanted. To have every Pokemon, minimally required over 70 friends who all played Pokemon and you managed to catch online after they finished the game.
Festival Plaza/Something similar: I don't hate this feature. It doesn't really appeal to me, but I don't hate it. What I hate is that in Sun and Moon, they gated the online features behind it. If they bring it back they need to separate it from PSS.
Overworld Following: I like my Pokemon as much as the next person. We wouldn't be here if we didn't. But sometimes I don't want to look at them. If the feature does make a comeback in the future, we need the option to shut it off.
Things I Do Not Want Back:
Unskippable cut scenes. I love stories. I especially liked the S/M story. I did not like, when attempting to SR for a female Popplio, that three minute choosing cutscene. It was cute the first ten time. But when RNG hates me, I get sick of it.
Version Exclusive clothing/colors: As I already mentioned, I like my clothes. But let the version POKEMON exclusives pick the version for people, not the clothing.