Its a bit different from Souls games. More of a straight up action game than before. I wasn't aware you level up weapons as >>15555109 says. I guess it will work like other action games, you unlock more moves, better versions of moves and get little damage increases.
Prosthetic arm looks cool, but is ultimately a neat gimmick.
We're definitely getting something with the moonlight sword. Its always been a greatsword though, so perhaps there will be some gaijin Samurai to wield it.
No hats I guess. The character will likely not have armour/clothes to change.