I'd be happy to see more multi-character games as the series continues. I'd take Akiyama leading a cast of newcomers, with cameos from Saejima, Majima and friends.
I feel like I prefer Yakuza 0's setup. One character gets samey, four characters feels crowded, two characters splitting the story and having different styles felt great.
In Yakuza 4, it was a relief to play as Kiryu because I felt like everyone else was lacking in some way in battle. It also didn't give anyone besides Akiyama and Saejima (thanks to Majima) time to breathe.
With Yakuza 0, the bouncing narrative felt good, I felt both characters had good stories, and I liked both their fighting styles.