My opinion for what it is worth is that fudoshin is a state of mind achieved after many, many years of practice, but not a visual goal that you aim for at a specific level.
It is a spiritual thing, totally calm and determined that lets you face your opponent with extreme courage but without going crazy. This is a state that some martial artists (soldiers of war) achieve - a sort of state of grace, but probably only in moments of extreme trauma and danger.
I would like to know more about fudoshin. I think I have experienced it from time to time but I cant call it up at will.
Osu
Trevor Gilbert
("If I had to select one quality, one personal characteristic that I regard as being most highly correlated with success, whatever the field, I would pick the trait of persistence. Determination. The will to endure to the end, to get knocked down seventy times and get up off the floor saying "Here goes number seventy-one" - Richard M. DeVos)