Leaving aside all of the will he / won't he come here views -- I am more interested in how he fits.
Could he and Melo co-exist? Could he play Shooting Guard? If so, then maybe he is the ONLY additional piece we need, if Galloway/Grant or somebody like Dellavedova can give you 3-and-D at PG and then let the offense run through our wings? If this works, then you really need only 2 players out of AA, DW and LT off the bench. This could also explain some of the supposed Knick interest in Nick Young -- he is locked in at $5M per already and could be a great defensive specialist. Plus, if you move DW for him now, then you have your bench wing locked up without adding salary -- thus removing the uncertainty of whether DW will opt-out and how much Lance might cost....
Alternatively, what if you keep AA at the 2 guard and have KD play SF? In this scenario Melo is your full time PF. You can either play KP 50/50 at PF/C
OR: You could consider making KP your full time Center and trading ROLO, to replace him with a cheaper backup for 16 - 18 min per night (maybe even a combination of KOQ, Amundson, Willie or Seraphin)? As much as I love Lopez, moving that contract creates LOTS of space to add Durant and round out the rest of the team with a very capable bench.
As a final question -- how would you compare / contrast the fit of Durant vs. Batum? Obviously Durant is a much more special player -- but in terms of fit, who has the most potential to transform this team into championship caliber?