I know there is a topic of what you are afraid of seeing in FFXIV , and after a quick scan I didn't see a topic like this so I figured I could start one. Forgive me if I missed it...
1)Something I'd really like to see carried over is Level Sync.
I know, I know, the new class-less / level-less system is all everyone is talking about, but you don't expect anyone to believe that your going to grow your character at the same pace fighting enemies in "starting" areas as opposed to harder to reach places.
Therefore, I'd like some way for people who have been playing for a short time and have gained some growth to head back and party with someone who is just starting out without having to put their character's growth "on hold"
2) Campaign. That was fun! Especially just before I stopped playing FFXI. When what you did was rewarded at the end of the battle. I don't even mind the idea of needing to build all the way up in order to survive there. That was part of the fun. It was something fun to do, alone or in a party, end game that didn't need hours of planning.
3) Crafting. I know it's been talked about, and I never got into it much in FFXI. But I'd really like to see it return and maybe be expanded on. Maybe if you make armor, you could customize it to let the world know your the crafter. A specific design or color... I think that would be great. How great would it be if someone in your linkshell was known for making awesome green blades?
That's all of the top of my head, I'm sure theres more. I just don't want this to become an illegible wall of text.