Many of us have probably forgotten that square used to make fighting games, well i for one would love to see them return. I'm not exactly sure where square-enix stands financially at the moment, although i'm sure they're not in a rush to make risky leaps. However, Bushido Blade and Bushido Blade 2 were fighting games that carved out their own niche in the genre. With the current revival of fighting titles, this one would blow up in the face of gamers like so much dynamite.
Bushido blade was a title that utilized slower moving, more calculated, and careful controls to win a fight that usually was settled by one strike of the blade. I'm not going to call this realistic (theres a move where you can jump 15 feet in the air over your opponent), but when it comes to video games, this is pretty close. The tension of needing to plant one good move, the, knowledge that one failed defense would lead to your humiliating defeat created a title that was not for the soft of core. This is perhaps why it never picked up steam, it was incredibly difficult to begin, and even more difficult to master. At the time, the environments were staggeringly large for a fighting title, nowadays, the fights could stretch even larger environs, possibly incorporate group battles, and seamless level transitions so that the tension of your ever in danger thread of life could be carried throughout a campaign.
Another thing that the two game series did well was having colorful and often times eccentric characters that you wanted to learn more about, which was only achieved through the single player campaign, where you discovered the relationships between each character and both sides were actually quite complex and interesting. (I forget their names, but the symbol for one side was red and one was blue in respect to the oldschool model)
There were also multiple weapons to select from at the beginning of a fight, of course some were naturally suited against others, while some characters were more adept at particuular weapons (having more or unique moves, or being faster with it).
Overall these were unique and deep fighting titles that i think could be revived with great success.