I know I'm being snarky, but when I read your post, my first thought was, "yeah, he would have helped us set the all time record for fewest team assists".
Remember the way everyone was bitching about being last in assists, too much iso ball, etc. I don't think having all of our top 3 options being iso-centric players would have helped the situation. In fact, in that regard, Melo relies MUCH more on the iso than Dame and C.J. That is, and has always been his game.
Unfortunately, he has gone from a high-scoring ball stopper who doesn't play defense to an incredibly inefficient ball stopper who doesn't play defense and makes $27 million a year. This isn't 2008 (circa 2008 Nate McMillan would have LOVED him). The game has changed, and Carmelo hasn't (well, other than getting a lot worse).
I honestly think he would have made us worse. Think about it. OKC added both PG13 and Melo. They won 1 more regular season game and 1 more playoff game. Paul George had a solid season and made 3rd team All NBA. George alone should have been good for another 6 - 8 wins. So, in my estimation, Melo actually cost them 5 - 7 wins. George was +2.6 BPM and Melo was -3.8 BPM. Anything Paul George added was more than offset by Carmelo.
No thanks.
BNM