Not quite what you're asking, but I've recently been playing a game on Normal as Chokosabe whereby my main force is a 20 unit stack of horse archers (well, 19 + a general). It was based off an off-handed comment by somebody that horse archers seem to auto-resolve well in TWS2, and so far it seems to be true. I've found that when auto-resolving a castle assault against 800 or so troops of mixed samurai and ashigaru you can expect to take anywhere from 0-80 casualties (out of a total force of 1200 cavalry), which is significantly better than I'd be able to achieve myself. I haven't tried personally fighting any battles with this force yet though, and I'm yet to run into a primarily samurai army of a similar size to my own.