On a side note, a Bleach "live - action" style movie may be quite interesting, as long as there were not toooo many special effects. A much, much slower pace and focus on charactersation being the order of the day - as that is what, in my opinion, made the series' stand out.
On - topic: For Keanu to pull this off, would require a vast departure from his usual acting style, which would certainly endanger his acting history of "almost every character for every role" - oh, aswell as taking a chance on actually immersing himself fully into a role.