Unless he's toast physically, Gordon Hayward is way better than CJ McCollum, imo. Foremost, he's way bigger, on a team that's undersized to begin with. CJ's basically an older, smaller, right-handed D'Angelo Russell, only without the passing skills (which is probably DLo's best quality). And as others have noted, a minuscule backcourt of Walker and CJ would get roasted defensively.
If you're angling to dump Hayward, I suggest finding him nice home in the Bay Area, where he'd slot in beautifully between Splash Bros and Draymond, and grab a boatload of young assets and picks from Minnesota or New York for DLo. Or heck, just keep DLo, who as noted is a bigger, better, younger version of CJ who could grow into his prime with the Jays as Kemba ages.