In a vacuum Miller would be a great fit for the Leafs, but team chemistry is always a consideration and Miller is a big personality. The Leafs current leadership group strikes me as more deferential and confrontation-averse than most. It would be a big risk to bring in a guy like Miller IMO and I would be surprised if management thought it was worth it.
I guess in your scenario it would only be a quasi-rental, which somewhat reduces the risk involved. Still, if I’m Toronto I’m looking for someone who will mesh better with the guys there now, and probably cost less as well.