The only guys Id even look at with a max are Hayward, Millsap, Porter, and Griffin.
Im not sure Porter is worth it, I expect Hayward to stay in Utah, and griffin is a huge injury risk. Milsapp is a risk due to age.
Its not a horrible idea to punt on cap space and extend this group. Give Isaiah a max extension, try to extend Kelly 4x10 and then use bird rights to resign Marcus and AB.
Then leverage the draft picks to fill the holes.
I think ultimately 1 of AB or Marcus gets traded. We pursue Hayward and Millsap in FA and then we max Isaiah give Kelly a deal most people initially hate but then come to realize is a good deal over its duration. After that we resign whichever of Marcus/AB that we didnt trade and move forward with that core:
Isaiah, AB/Smart, Al, FA(?), Brown, Nets '17, Crowder