Armoured samurai and Shinsengumi be useful for the conflict (both on the Shogunate side), but in a limited number, the Shinsengumi mainly because they were a small force.
In the Battle of Toba Fushimi a big number of samurai armed only with spears and swords charged against the Imperial troops of Satsuma.
By the way, I will make Shinsengumi, working on his design.