I'd do this. Building through free agency actually becomes a viable option with both KP and Kawhi the team. It's not a Melo type of situation to me because frankly, Kawhi is way better than Melo ever was ( no slight against Melo), he's probably the only guy in the NBA who is elite on both sides of the ball, and he fits with KP, unlike Melo who didn't really fit with Amare initially. He's the only guy in the NBA I would give up multiple firsts for and not have a hint of regret over it. If Kawhi gets traded to another team that he's at least okay with, he's probably not turning down that supermax to sign with the Knicks next year.
KP, Kawhi and another top tier free agent is fukking up the east imo ( Imagine signing Jimmy Butler in 2019 to add to this squad
). I understand not doing it though of course, but signing a top tier free agent is a lot less likely with just one star on the team.