Street Fighter X Tekken, namely the Gem system and everything it stands for.
"For future titles I want to keep having this concept of, my character is different than your character," Ono said during an interview with Eurogamer. "In fighting games, the only difference between me and you is how good I am. But what I want to do with fighting games from now on is add in that element of customisation [sic], where I can have a Ryu that's different than your Ryu, so we can compete on a different level than just our execution."
Ono envisions a future where players can modify their characters on a deeper level than SFxT's Gem system allows for. "It would be like, the Ryu that Yoshinori Ono made is the best, or the Ryu that other guy made sucks." Ono did not go into any specifics regarding future titles, but it's clear that he wants to steer the Street Fighter series away from the character selection screen and toward the stat tree.