Samurai armies are problem army. There are a limited number of enemies they fight, Korea and Mongols. For the most part they fought themselves. Which means you would be painting both sides and hoping to host or run convention games.
My plan to get around this and get the most usage out of them is to run them through the 3 rule sets above. The high frequency use is Warmaster. It is fairly easy to get 6 games in a year between the PA, NJ, and NE groups. Con games Warmaster Ancients, because it is easy to learn, fast paced, and less likely guess players will get board during the game. Killer Katanas is painful to get through. This would be the house hosted event and would represent samurai warfare less abstractly as the other two.
The next problem is cavalry. The samurai never had a cavalry force as we "westerns" picture cavalry. The Japanese never had a proper western cavalry force until the war with Russia. The famous Takeda and Kai were known for their strength in Cavalry. Yet they never used them as cavalry. The usage is more compatible to chariots (battle field taxis), mobile infantry.
Wargaming the samurai period Vs non samurai armies or armies they would have never meet creates a problem. You as a samurai player will face a problem against another army that has a proper cavalry force.
During the time of the samurai, the horse in Japan was much smaller. It could only carry a full armored samurai at a walk or the speed of a man running/trot. It was not big enough for cavalry operations. The hollywood samurai cavalry charge was never possible.
Those mounted samurai would have had to practice cavalry maneuvers and charging to be effective. The mounted samurai never trained together as a cavalry unit.
Also the samurai were retainers, feudal lords of a village or area. More like the roman system of patronage than a feudal system. The people they took to battle were the same individuals that worked the rice paddies. No retainer or lord was about to give up control of his men to ride in a mass cavalry unit. While the rest were feed into battle by someone who didn't care or would not suffer the results.
The real deal is the mounted warriors had infantry running along side them. Much like the Celts or Germanic tribes.
None of which matters at all for Warmaster. As the Nippon list is an anime bullshit. So on to painted dudes;
6 stand of Ashigaru, 2 units. The whole army will get based together in an attempt to maintain uniformity across the bases.