First Agito+ needs to be released. They ran into development problems and delayed it indefinitely in Japan. Rise of Mana also ran into development issues, but apparently recent Unity updates helped them push through it. So Agito+ is probably next.
Yeah, I was a little worried when Sony was promoting Unity engine as Vita's great hope, yet clear trends quickly emerged when titles using it started being announced. (Basically, a ton of 2D games quickly jumped on-board, but fully 3D games were slow in coming, and games like Oddworld New & Tasty or Assault Android Cactus either were delayed or reported difficulties.) (You can see a list of
Vita Unity Engine games on the Unity site, and of those actually shipped, I think only Counterspy is 3D and it didn't run so hot. Deadman's Cross also apparently had some tech issues.)
If Sony is going to lay off of producing AAAs for its own platform and instead push for acquiring a base of indie/3rd Party support, that's one thing. But if that's the path, and if Unity Engine is the key, they need to provide some assistance to Unity in making that thing run as well as possible on Vita.
Square doesn't seem swayed by FF X/IX Vita sales to bring other top titles such as FF Type-0 HD to the portable,
but it has quietly upped its support of Vita with conversions of its cellphone line (Chaos Rings, Deadman's Cross, Agito+ and Rise of Mana.) There's some decent product in that catalog, and more and more is on Unity (including big stuff like Mobius Final Fantasy and the DQ VII port, plus SE-UK stuff like Hitman Go and Deus Ex: The Fall, albeit some maybe too big to consider for Vita at this point) so Sony, Unity, get together.
The Vita audience is completely insignificant in comparison, and either way it will be a F2P service game they have to keep running. So might as well run it for the platforms where audiences are actually on.
F2P seemed to work a bit on Vita with Toro's Friend Network, there were a lot of people playing it and buying costumes when I played it, though that was a long time ago. There's certainly a ton of product trying F2P on Vita (even if a percentage is cellphone ports or cross-platform console releases) so somebody thinks it's a way to make something of this tricky market. I suppose it'll depend on how easy it would be to convert the translation script from Agito mobile to Agito+ (if Agito ever does get that localization) as to whether Square will release that version outside Japan.