I hope the crew improve, either in fights or after the battles. Ideally if they don't get haki mid-battle (the ones that don't have it), them recognizing that that's an issue and learning it post-battle would be nice.
Luffy: Improved G5 time limit and VOAT/observation haki improvement if Oda wants.
Zoro: He seems pretty well-rounded and I'm not sure if Oda would have him struggle to prompt a power-up. Maybe just new moves to show he's always working on something.
Sanji: Future Sight is the main one I hope for. If he can't use whatever Gaban used to overcome regen then that as well.
Jimbei: Not sure, he's pretty well-rounded and I'm not sure if Oda will have him get a serious fight this arc, but it'd be nice.
Franky, Robin, Brook, Chopper: Armament haki.
Nami: Observation haki perhaps to prevent close calls like needing to move on his own after a missed hit. I like that she's a glass cannon.
Usopp: Armament haki should improve his offense and consistent usage of observation haki should put him on the right track.