I tried this several times and came up with a couple different scenarios. I couldn't even get to first base! This took a little trial and error but I found out how to at least get a good workable start on a long, legendary campaign playing the Mori clan. I have completed a campaign as Mori on normal difficulty and although fun, it was way too easy! So I tried it on hard, very hard and legendary difficulties and was so surprised at how difficult it was. I chose them because even in Shogun 1 their starting area was my favorite area to play.
I chose Mori as the clan to play a long campaign of legendary difficulty.