Changing now would obviously be infeasible because the vast majority of the English fandom has always had these names, and to change now would cause problems. Even if we could go back in time and change it, I wouldn't want to. This is because all the English ones have etymologies that can be traced more easily, whereas some of the Japanese etymologies wouldn't make sense. I will concede that some Japanese names are better, for example, as Berlitz said, "barrier'd" over "Mr. Mime", as far as females are concerned.