With all the attacking talent Dortmund are hoovering up, I doubt, when fit he be anything but a bench warmer there!
But, if we can nab him on a Loan to buy deal then I wouldn't say no, he "was" a quality player, played his best under Klopp and maybe he knows what to say and do to get this boy playing at that level again.
A Loan to Buy deal (with a fee agreed before loan at a reasonable level) really is Win Win, if he comes and doesn't do well, we ship him back, if he does well, then we get a world class player on the cheap..