Tekken producer Katsuhiro Harada has explained that Tekken Tag Tournament 2's content is mainly driven by player feedback - with an estimate that puts that around 80% of the final product.
"Tekken 3 - sixty percent was development team driven," Harada-san explained. "We didn't really listen to too much: we wanted to do this, so we did it. For Tag 2 its pretty much eighty percent that's based on feedback of what everyone wants, whether it be character choices or gameplay mechanics, content that should be suited towards advanced players, or content for novice players. All of these things were taken into account when creating it.
"The extra twenty percent was on top of all that, ideas that we had for shocking or surprising the fans - in pleasant ways. The focus is quite different depending on the game."
The Tekken producer talks at length about the game's creation, Fight Lab, and re-introducing characters the team don't even like in our full interview which you can read here.