Going to Leipzig would be good for him. I understand his desire to stay at his dream club, but if he has another season similar to the last one, his value will only further deteriorate. He's been here for two years now and besides the little purple patch, he has hardly shown anything to suggest, that he has the quality to succeed at this level.
Nonetheless he is entitled to refuse a transfer and try to fight for his place. I just hope his agent/advisors know what they're doing and don't set him up for failure, by having him sit on the bench for the next few years. He really needs to play, if he wants to improve.