You probably can't trade CJ for a wing you like today. You have to trade him for a project wing that might look good tomorrow, a post-hype, pre-production wing most likely. Examples of these recently include Brandon Ingram and Andrew Wiggins. They were past their hype phase, but hadn't really panned out as productive players. Ingram wasn't overpaid yet, so he was more valuable at the time of trade, but not a hugely valuable player. Wiggins was overpaid, but the Warriors traded a very CJ-like player in DeAngelo Russell--also overpaid for what he provided, but Wiggins was a superior fit for Golden State.
Nobody would have been too thrilled with either Ingram or Wiggins at the time of trade, but either player would make Portland better in place of McCollum, IMO. That's the type of wing to look for, because any wing currently playing well isn't going to be dealt for McCollum, IMO.