I feel like they need more going on here for the Samurai, the one class feature just doesn't feel like enough. He should get a few more bonuses, I mean since you guys are going more in the historical direction. It would fall in line well as the cavalier gets bonuses to charge so too should the samurai with mounted archery.
Just make it easier for him to hit and run using a longbow with ease while mounted. And maybe some damage increases for move and shoot tactics seeing as there isn't a charge like multiplier for ranged. And samurai did train and use firearms but that might be venturing into territory that you don't want to go.
Just my thoughts on the Samurai.
