You know. Take the Witcher and Deus Ex's philosophical and social commentary, mix in the black humor and amorality from Vampire the Masquerade, add a little psychological uncertainty a la Spec Ops: The Line...
And then the Tales combat system, techs, skits, and all that.
"Yesterday we obeyed kings and bent our necks before emperors. But today we kneel only to truth..." - Khalil Gibran
The notion of it bores me personally. I like my games light-hearted and fun. I generally don't take things seriously enough to buy into the 'darker' stuff.
It just wouldn't be what I've come to expect from the series. Why would I want to drastically change something that I already enjoy so much as is? I could just play another series if I want a completely different experience.
Xillia 2 is the darkest one. It also the one with the best story in the series. I don't know if I want more Tales games like that. It was so sad. Even now, I'm still sad. That game made me cry so much.