I kept a two each of revolver cavalry and sabre cavalry in most of my stacks for rapid defense and exploitation and that seemed to compensate for my lines poor maneuverability and inflexibility. Especially after unlocking the Kneel Fire drill Nagaoka riflemen are capable of simply mowing down most opposition. I found myself phasing out traditional units within the first 15 turns. The bonuses only get better as you unlock more modern units and financial techs. Their boost to financial buildings and modern troops (particularly rifles) makes developing quickly a real priority.
Just finished a normal/short campaign with Nagaoka to try them out and I've got to say I had a lot of fun with them.
