I don't know much about video games. My interests are mainly in writing. Here goes:
I hope Velvet has some grit, but also some flaws. I prefer my Tales protagonists to be slightly cynical (Yuri) and/or flawed in ironic ways (Luke) rather than the idealistic adventurer/country folk types (Stahn, Reid, Shing, Lloyd, Asbel, et al). The "lost her smile" plot intrigues but also makes me suspicious, since a woman protagonist deserves more than her smile as a character arc. But the "tragedy in her past" plot is promising. I hope it's completely brutal.
I hope that the other members of the party have serious internal struggles. This one is slightly more complicated. The series is generally good at having character plots pay off, but some are better than others. I like the characters who are forced to introspection by consequences of their world views (Jade, Alvin, Judith) or characters who lose their naiveté through violent wake-up calls (Philia, Chalcedony). I also like it when characters have to defeat somebody who hurt them, but I prefer the conflicts that torment the characters (Natalia, Ines) to the ones that set up arbitrary rivalries (Leia (and don't get me wrong, Agria is actually one of my favorites in the series)). I don't have a problem with "quirky" characters, but I would also like to see them in serious conflicts and dilemmas.
I hope the main villain has an ideology. This one may be controversial. Everybody has different tastes. I don't really like my villains to be complete sadists. My favorites are the dangerously passionate villains who justify utopian ends through absurd means (Van, Duke, Gaius). I love to see the characters argue over ideology. I love the part in Abyss where the characters argue with Van about logic and causality before fighting him, because it raises questions that are at stake in the fight. Largo the Black Lion says something like "this is a battle of ideologies" at one point, and I loved that aspect of the game. Also, why not a lady-villain?
I suppose those are my big three.