So I'm going to detail my idea for a T7 back before and during TTT2's release. I had honestly really wanted a job at Namco, even as a freelancer or something, to make this happen.
-an unconscious Jin was saved by Zafina and brought back to her village to heal.
-there he finds his mother, Jun, helping him recover and his Devil gene removed from within and sealed in a crystal ball after defeating Azazel.
-Heihachi, sensing the "cleansing" of the Devil gene, retreats to the mountains to live out the rest of his life in peace and tranquility in solitude.
-Kazuya barely clings to his sanity upon losing the Devil inside of him (sealed when Jin defeated Azazel) as he realizes all of his actions, deeds and glory were the result of something other than his own innate skills.
-he attacks several people on the way to his estate and locks himself inside, continuing his descent into madness.
-Lars, wanting to know more about his bloodline, seeks out Heihachi in the mountains.
-Heihachi welcomes the company and the two train and meditate together while catching up and sharing tales.
-Lars mentions how Jin had been found and that the Devil was sealed in a crystal, thus ending the chaos.
-Heihachi, intrigued by this news and impressed with Lars' skills, decides to host a Tekken League*.
-He secretly hopes to lure Jin in an attempt to discover the whereabouts of this "Devil crystal".
*So this new tournament is set up more like a league in sports. Teams of three are separated by regions, each having their own home fighting stage and home crowds and play to reach the playoffs and championship fight based on their W/L record. Three fighters per team, two per fight (tag style) with one on the bench who can be swapped in and out between matches. Characters with the lowest health after a match don't fully heal thus giving incentive to swap them out, but it could be your better character causing you to rethink benching them. Crowds provide meter boost, cheering damaging counters, combos, unblockables and other special moves. Meter is used to perform special partner moves with unique animations. Story mode has predecided teams and home turfs while arcade and MP, of course, have customizable teams.
Why three characters per team? This was to help segue into a new cast. For example, Nina and Anna partner up with the daughter of a friend of their father. She possesses traits from each of them and her own original style. So a Tekken 8 could feature this new chick in place of Nina and Anna to progress the story that no doubt reunleashes the Devil into the wild or has fighters fighting in a tournament proper for control of the crystal (complete with their endings showcasing what they'd do with said crystal).
I'm not going to get into each idea I had for new characters and teams and whatnot. I just wanted to provide my general outline for the "main" plot thread and basics behind the new system I thought up. Would you have wanted these ideas in a Tekken game?