It would be an eeeeeeeeeeeeeeeeextremely risky signing. Personally I wouldn't go anywhere near him. If, and its a huge if, we can get him for 1.5-2.75 million it MIGHT be worth a punt.
He had a monemental breakthrough when he was about 18. He was he next Reus etc. However definitely last season and the majprity of the season before that he has been simply woeful. He has been depolyed in a number of positions as Stuttgart try and revive all that promise he showed right at the start of his career.
We'd be buying a player that had a spectacular run of 15 games about 18 months - 2 seasons ago, and who has produced very, very little since then, and is far from a regular fixture in a team that just about avoided the drop. For example, Martin Harnik is a far far better player, and I'm not sure anyone would be clamouring to sign him. I'd leave well alone on this one, but I'm also sceptical that we have any genuine interest in him anyway, as the scouts will have seen his progression hit a brick wall.