Winning Influence
If the Clippers bring in Melo, CP3 is all but guaranteed to stay. The two are very close friends and have both expressed interest in playing together at some point in their careers. This would be their only real chance at making that happen.
Not only does adding Carmelo help with bringing back CP3, it also helps you fill out your bench. As close to the luxury tax that the Clippers are, most of the bench will be comprised of Vet minimum players. The Veteran NBA players that are still contributing are ring chasing, adding Melo would make them one of the better teams in the NBA. Players would be lining up to join the Clippers ride to a Championship.