So after investing about 55 hours into this, I decided to dabble in some mods. Here are some really good ones that improve the game quite a bit:
Shogun 2 Realism Mod - i'll start with the biggie. This mod adds too many small changes to list, but which add up to make the game so much more fun to play (ironically for something aiming to make it more realistic). I find that with this mod installed, the game flows a lot more naturally and feels less artificial. I've felt a lot less like I was restricted from doing certain intricate actions just because of some of the vanilla game's silly rules. Other little perks are the greater distance which your army retreats to if attacked, and being able to fight some besieged battles on the field. You need to make sure your PC can handle this mod, as it has a huge benefit of bigger unit sizes, and therefore more epic and long lasting battles.
Realm Divide mod - one of the worst flaws which holds the vanilla game back from perfection is the dreaded 'realm divide' mechanic, when everyone including best pals turn on you because Kyoto gets jelly. This mod
mostly corrects it, so that the most people can possibly hate you because of it is -60, which also lowers in each successive turn. So now your very friendly clans will stickwitu. Just.
Shogun 2 Total Music Mod - now don't get me wrong, the Shogun 2 soundtrack is fantastic and arguably the best all year. However, if you're like me, the same tunes over and over can get tiring. This mod exchanges 95% of the music with a mix of tracks from the original Shogun and some surprisingly fitting royalty-free music. Some of it is really quite special and has the benefit of not breaking any copyright laws.
Deployable bamboo stakes - no idea why this was omitted from the game. This allows all bow units and a few other types of foot soldiers to deploy a line of bamboo stakes, which helps tremendously to protect against charging horses. This makes the game a bit more tactical I think, instead of mindless slaughter.
Unit variety mod - if your PC can handle ultra quality units, this mod is perhaps the best aesthetic one available. It ensures that every unit on the battlefield is unique - something like 3.5 million different combinations. It makes zooming in even more of a pleasure.
Rankfire for all bow units - a minor mod. This allows all bow units to use the ranked fire stance that not only looks the part, but also makes volleys more frequent. Provides a useful edge on the battlefield during the very early stages of play.
Retextured Battle UI - a subtle but nice aesthetic improvement over the default battle interface. Tanned parchment > white parchment!
Japanese speech fix - another subtle mod which I doubt people will really care about. This fixes a few errors in the translation of the game's dialogue. While 99% of people won't notice the difference, it's nice to know that what you are playing is totally accurate.
All credit goes to the original authors of these mods. They truly re-invigorated the game.
Also do not forget about the awesome Rise of the Samurai DLC out this week, which promises to add a substantial amount of new gameplay. I can see myself reaching 100 hours of play soon enough.