Anyone whos watched Japanese wrestling matches, especially live, will know that its a hard physical style. There are lots of kicks and chops. Striking is a large part of the arsenal of a Japanese pro wrestler, together with suplexes and hard landings. This does not mix well with the WWE style of working as safely as possible due to the heavy schedule that has already been mentioned. While some wrestlers, especially those with Japanese experience of their own like Rob Van Dam or Daniel Bryan, will probably be fine with it, its easy to imagine that there will be some of the top level stars who wouldnt want to have to take the risk of getting hurt ahead of the next nights show. Furthermore, they are the guys with the influence in the dressing room, so upsetting them will rub off on the whole roster. Having said that, Daniel Bryan has managed to tone down his much stiffer Ring of Honor style offence for a realistic looking but easier WWE style offence. CM Punk has done this too, so it can be done.