Hey, so I remember my first 10K game. I was all ready and used to those 5k games and enjoying them quite a bit. They were very intense and fun. I had armies saved for 5k and had no idea when I would jump up to 10K so it took me totally off guard, I was lost, and on top of that my opponent was nice enough to ready up as soon as we connected so I didn't have time to think out my units. I just took a larger version of what had worked for me in the 5k battles: ashi spears, ashi bows, and 2 yari cav. Needless to say I got stomped, was not happy.

But I've learned, and I expect you will too. As someone who enjoys going archer heavy and likes to win the skirmish battle please note that bow samurai are your best enemy and worst friend. It doesn't take very many upgrades for bow ashigaru to just be better than them, when vetting bowmen always focus on accuracy first as I believe that it doesn't matter how fast your guys shoot, or how much damage they do, if they aren't hitting the enemy then they aren't doing anything. I found that after maxing their accuracy upgrades they can easily outshoot unvetted bow samurai for much less the price, and even if they can't win if your general is nearby they will usually eat enough arrows to protect your melee guys.

As for your specific build go with what you like, feel free to experiment and have fun losing/learning. Don't get frustrated and pay attention to what your opponents have. Always go for a balanced army as those are the most reliable, and most fun to play with/against.