The best case scenario for LeBron James this off season is going to the Boston Celtics.
They are perfect for each other. They need to make this happen - even if it means trading Kyrie Irving.
Let's start with why it is perfect for Boston:
The Aging Superstar with Up-And-Coming Talent is Proven Success.
Adding LeBron to Tatum, Hayward, Horford, and those other young players would turn Boston into a dynasty. They would undoubtedly win several rings and continue to contend after LeBron declines/retires. Look at these examples: Kareem and Magic. David Robinson and Tim Duncan. Duncan and Kawhi Leonard. The nearing-the-end-of-their-prime superstar paired with young talent is a proven recipe for success.
LeBron fits perfectly with Boston's Tatum, Horford, and Hayward.
Brad Stevens will surely be starting are Horford, Hayward, and Tatum. LeBron as the forth starter would make this team perhaps the most versatile team of all time. LeBron can play that "point-foward" roll of bringing the ball up and initiating the offense, thus allowing you to start a defensive player like Marcus Smart or a center like Morris or Baynes. Or, LeBron could play off the ball, allowing Stevens to start a point guard like Kyrie, Brown, or Rozier. Ultimately, these four main players gives Brad Steven's the freedom to plug in and rotate players however he wants; regardless of position.
Kyrie's contract is perfect if you have to move him
Kyrie does not have a no trade clause. He also only has one more year left on his contract. This makes moving him easy. Here's a question I've heard: Are the Celtics better off starting Brown or Rozier than Irving anyway? The fact that this is even a legitimate question makes moving Kyrie for LeBron an easy choice. Kyrie's bad defense makes him a borderline starter on this Celtics team with player like Jaylen Brown and Terry Rozier that are already better on defense, getting better on offense, and play the same position. With LeBron James instead of Kyrie, you've upgraded on both sides of the ball.
Winning championships is what both parties want, so let's now transition into why Boston is perfect for LeBron.
LeBron has never played for a great coach.
Besides the obvious "best chance to win rings," there are other perfect benefits to joining Boston for LeBron. The first one is playing for Danny Ainge and Brad Stevens. LeBron pretty much had to bring an entire new culture to Cleveland to make the Cavaliers a contender. LeBron had to help the front office, the coaching, and also carry a huge load as a player. That sounds exhausting. Finishing his career with Boston would mean being able to focus on being a player, and at most a "coach on the court" where he helps Stevens carry out the game plan. All the other stuff would be covered at a high level. Stevens would be far and away the best coach LeBron has ever played for. And Danny Ainge is one of the best general managers in the league. Stevens would make a great system that includes LeBron and worry about the parts of the game like when to call time-outs, leaving LeBron free to focus more on being the best player he can be.
LeBron would be "the guy" at first and then transition like Kareem and Duncan.
LeBron would be joining a team without any MVPs and, if they did end up trading Kyire, a team without any championship experience. LeBron could to go Boston and LEAD them to a ring in the next year or two. Then, as he gets older, watch the other Celtics step up and carry more and more of the load. And then, like the Lakers did for Kareem and the Spurs did for Duncan, LeBron could still be contending for championships at 40 years old because his team being able to carry a lot more of the load.
Defense Wins Championships.
Plain and simple. Boston was the best defensive team in the NBA last year - especially after Kyrie Irving got hurt. All the greats had great defenses. Michael Jordan had Pippen and Rodman. Kobe had defensive-player-of-the-year Metta World Peace for his last ring, and Shaq for his first ones. The Warriors are a great defensive team. The Celtics would immediately become the best defensive team LeBron has ever been on.
Stay in the East
This is a lesser reason but a good reason none-the-less. If LeBron were to go West, he would have to go through Golden State before the finals. He would have to go through Houston (if he didn't join them). Other teams like the Jazz are one piece away from being very good. You think the East is worse than the West now? Imagine if LeBron left it. That would destroy the balance of the conferences. LeBron staying in the East keeps the conferences closer in strength and makes for a better finals.
In conclusion, LeBron and Boston are perfect for each other - regardless if they to give up Kyrie in order to make it work. If Boston's goal is to become a dynasty and win championships, their best move it to bring in LeBron. He completes their starting line up and brings a perfect balance of experience to their young core. LeBron would benefit greatly from Brad Stevens and the Celtics front office. He'd be joining the number one rated defense. He would have as high a chance as anywhere (except joining the Warriors) to win championships, all while not having to join up with any other current MVPs. He would set himself up to transition from carrying a team to just being a part of the team like Kareem and Duncan as he gets older. And with the cherry on top being able to stay in the East.