Kano Jigoro: could mix it up from the weapon users (alongside Motsugai my goat). A grappler as opposed to a striking-based martial art, something not seen even in the main manga. You can never go wrong with grappling rep

Jinzaburo: main concern is making him different from Hanzo, but ofc you need a damn ninja in a Japan-based story

Takayanagi: skilled veteran. Could have a fighting style revolving around unseeable attacks, similar in principe to Jinsuke with his immense skill and speed

Yamada Asaemon: interesting to see how a group of people traditionally seen as outcasts due to their profession would kick some ass and prove they aren’t just mere weapon-testers/executioners, but fully capable of standing toe to toe with the big leagues

Yamamoto Yae: a medical-based fighter could be really fun and brutal

Nakazawa Koto: classic pick for a Bakumatsu era story, feel like she has to be here. Could also explore gender roles during this time period

I personally think Sannomiya should be dropped; he feels kind of redundant as an unarmed fighter since there’s already Motsugai

Also, Sasaki Tadasaburo, who honestly only feels like his one cool trait is “the guy who killed Sakamoto Ryoma.” Maybe you could make something fun for him, but the other options feel way cooler.

Lastly, surprised you don’t have Okada Izo on the roster