This should be fun. The rumors concerning a Final Fantasy XIII sequel don't have much merit to them, but it's still fun to consider: what do we want to see out of FFXIII-2, if it actually existed?
The only other sequel in the franchise is Final Fantasy X-2 , which exists in a love/hate relationship world amongst the fans. Personally, I had no problem with it, although I certainly do believe FFX was better. I wasn't the biggest supporter of the story in FFX-2 but I loved the new class system (Dress Spheres), if only because it sort of reminded me of Final Fantasy Tactics . The rest of the gameplay was plenty solid and entertaining and if Square-Enix wanted to take a similar route for Lightning's return, I wouldn't mind at all. But of course, that isn't going to happen, because even the remotest version of turn-based is dead on consoles.
Still, it's not outside the realm of the possibility to think they'd change a great deal. I would prefer them to stick to the structure that arrived after we reached Gran Pulse in FFXIII – and I seriously doubt I'm alone on that – because it affords more freedom and makes it feel like an actual RPG. I would also want them to slow the combat down and re-implement some semblance of strategy. I keep thinking the system from FFXII would work extremely well; it's basically the same system we see in other hardcore RPGs, like Dragon Age . Then again, they could try something entirely new; lest we forget new forms of character advancement is something we always expect from every new FF. Maybe they could take a risk or two and give us something we've really never seen before…
As for new characters, I suppose that'd be okay. The cast in FFXIII wasn't one of my favorites, but I think they really can do a lot more with many of the main players. In fact, most of the characters were just starting to get interesting in the latter stages of FFXIII. But hey, I want Cid to be playable. I think the last time he was a party member was in FFVII; he's long past due. So, what do you want? If you were standing in front of the design team, what would be your ultimate directive? What ideas would you want to try? And try to be nice to the S-E employees.