Chark was not able to have a solid quarterback in any year of his career. This might explain the lack of consistency he has shown in the past season. Chark is coming off an ankle injury that forced him to miss a lot of playing time. However, the good news is that the injury happened in October, so he should be 100% healthy going into training camp.
If you pair him and Mooney as deep threats, you would help Justin Fields so much. We know how much Fields like to throw the ball deep and he would have two amazing pass-catchers to be on the receiving end of it. The fact that Chark has not been extremely productive and that he is coming off an injury makes him a middle-tier receiver in free agency, who could cost only around $10-12 million per year. He would make a lot of sense for what the Bears need.
Here he is making a great play against the Bears: