You want solid reasons that this will be bad?
How about pretty much every remake of a japanese film by an american company has been ok at best? That a good reason? Ok it could jsut be me, but the american remakes of the ring and the grudge just weren't as good. Heck either the producter or director, i forget which, of the grudge remake basically insulted the audience he was remaking it for by saying they wouldnt understand the original classics cause it lacked american people or culture...
But really, go and look back at the list of american remakes of foreign films and the majority are worse than the original, considering akiras status as a classic and its an anime been adapted to live action, the chances of it been good are questionable, but the chances of it been anywhere near as good as the original are so slim its just silly, especially considering the director hasnt really done much of any real note...