Det-Mil-Dal 3 way trade
Obviously a trade this large would be difficult to go through, but I can make a case for each team's perspective. Who says no?
Detroit - Josh Smith is an athletic swingman who can't shoot, whose effort has been questioned, and who does not fit with your two best players. That is not a good combination for a 28 year old who you are paying 13.5 mil for the next 4 years. It's time to admit the deal was a mistake and see if there is anyway you could get out of it. Very few teams would be willing to take on his contract, and you can make a case that it is one of the 5 most untradeable in the league. This trade would be a major step forward at clearing their cap sheet. Butler gives them another expiring contract setting them up to be able to pay Monroe, or to have the cap space to go in another direction if they so choose. Mayo has basically been a disaster for the Bucks, but has shown stretches of being an above average SG during his career. Plus he can shoot, something this team needs desperately. It's not a contract you would take on voluntarily, but it's a worthwhile price to get out of the Smith deal and at least has some potential to pay dividends on the court.
Milwaukee - You are the worst team in the league. Things have not been going well for you. On the bright side you have an incredibly raw athletic 19 year old who has star potential and are in poll position to land a top pick in one of the best drafts in years. Josh Smith is still a talented productive player, who is in a bad situation playing out of position. This trade allows you to get out a bunch of bad contracts (Mayo, Neal, Zaza) and take on smaller deals. Larry Sanders has been a disappointment since he signed his extension, and with John Henson on your team, is he really worth 11 mil a year? The top 3 picks in the draft would fit well with Smith/Giannis as opposed to Sanders who would be redundant if they manage to get Embiid.
Dallas - You are trying to stay competitive during the end of the Dirk era. You haven't been able to land a star in FA over the past two years. You have a chance to acquire a young player with potential who was an elite rim protector a year ago. The Ellis-Calderon signings have been better than expected, now you bring in Sanders and hope that he can pull off a 2011 Chandler impersonation and take your team to the next level. He is a dramatic improvement over Dalembert/Wright. They would still have financial flexibility to add a few pieces. Gary Neal is a throw-in but was solid with the Spurs two years ago and could be a nice piece.