I see nothing wrong with this move as it's entirely to do with improving your squad. Unless there are rules in place to prevent such moves (which I would disagree with), then it's fair game. It's a keeper league, so why should someone who's looking for the future be prevented from improving their team just because they are no longer in the playoffs? Furthermore, perhaps there may be other managers looking to pick them up as well.
All I've got...all I've got is insane!