Honestly it's style is not very different to Persona 4. So it could be done, but it would take some work, as I'm sure all the models and resolution are way too high. They'd have to go through and tone everything down. But I don't think the engine itself is "too powerful" for the Vita. Just models and textures are too intensive. If there were a wide enough market for it, I'd almost bank on them scaling it back and doing a port. But with the Vita floundering in the water, who knows