A team with Gobert, Gordon and Mitchell could maybe attract a decent FA as well, on a three-year deal that ends when it's time to max Mitchell. That said, Porter is likely going to be a better shooter than Gordon and could just as likely help attract a good FA.
Why is it likely Porter is going to be a better shooter? Gordon is a 40% 3pt shooter. The dude lights it up. It's not a fluke.