A little history lesson for people.. (not towards Potatoman, who I'm sure knows all of this)
The time period that Potatoman has based his mod on, the Sengoku Jidai (in English, the Warring States Period), Lasted for about 100 years, from the 1480s to 1600. In most people's minds, the Sengoku Jidai is even more closely associated with the Last part of that time period, with the 3 Great Unifiers of Nobunaga, Toyotomi, and Ieyasu.
Most of the suggestions you are giving Potatoman, regarding such things as the bow, mounted troops vs. unmounted troops, etc., are historically inaccurate. While it is true that in earlier times the samurai was a mounted archer (say, at the end of the Heian period where the Heike Monogatari (the Tale of the Heike) is situated, by the latter parts of the Sengoku Jidai period, the samurai was a foot soldier, much more akin to the Kurosawa film Versions. While the debate about mounts and bows is interesting, I'm afraid it doesn't really impinge on Potatoman's mod, historically.
For a good cinematic representative of Sengoku Jidai samurai, Ran is a good example. I think this is the feel, at least militarily, that Potatoman is trying to capture in his mod.
Regarding the bow specifically, it really is intereting. There is the daikyu, the asymmetric bow mainly meant to be used from horseback. That is the bow that most here have been discussing. However, there are mentions earlier of something called the o-yumi, or great bow. The funny thing is that no actual remains of it have been found. Apparently, it was a huge crossbow used as a siege engine that Japan imported from China after the Taika Reforms of 645. Basically, it sounds like a ballista to me.
Having taken 3 Japanese history courses Last quarter, and graduating with a degree in Japanese at the end of it, tends to fill your head with some of the most interesting trivia.
Bayushi Tasogare
Japanese 'Buff'