I have ideas for what they should do for a third title. Rather than being a direct sequel to the first game or prequel to the second game, could be a mix that allows you to play in both timelines a la Final Fantasy VIII courtesy of Squall and Laguna. In such a case, I could imagine, Sephiroth and Zack both being on the side of order (Cosmos) while Genesis and Angeal were on the side of Chaos. Other characters to hopefully add would be Auron and Shuyin (perhaps Paine), Gestahl and Sabin or Shadow, a Warrior of Dawn, Zemus, Xande and Goldor, Leon from Final Fantasy II, in 011 he would be a Chaos ally, whereas in 013, he could be brought back as a Cosmos ally, Final Fantasy VIII characters Seifer (Cosmos to Chaos), Kiros, Raijin, or Fujin, Garland IX as an alt for the original, and maybe Chaos from 4HoL as well... also Magissa, Enuo, or a Demon of the RiftMelusine, Necrophobe, Halycarnassus...

Another feature I'd like to see is more large enemies like Chaos and Feral Chaos. I'm talking some of the villains' transformations as well as side-bosses like Ozma, Necron, Guard Scorpion, X-ATM092, etc. I'm not saying they should be playable. Just have them appear once per quest. Guard Scorpion and Diamond or Jenova can appear during Cloud's portion, Necron and Ozma during Zidane's, etc.

I would also like to be able to alternate EX Bursts similarly to how you can choose your LIMIT Breaks in later FFs. WoL could have moves from the other job classes that were default to the game.

I also think Onion Knight's altfits should include Arc and Refia. For Refia, as a copout to have more girls in the game, they could tweak the dialogue to refer to the Onion Knight as "her" rather "him" etc. I think Ingus should be the default look. "Slasher" can be Luneth's look. Arc would don the traditional look. Of course, this is all assuming Onion Knight returns. I think some character from the past two games won't return in the next.

If Cloud returns, his KH look should be non-DLC. Minaba Zidane should also be "default", Squall should have a blonde alt as shown in some of his artwork, Tifa's Amano alt should have white hair... if Seifer, Raijin or Fujin get put in the game, they should have KH alts (even if DLC).