I think you have to have one regardless, and I think Drew can still throw bombs, just not at the high accuracy/ball placement he once had.
And this likely being his last season, it would be good to get one on the team and learning the offense. Also, if Taysom really is going to get more snaps, he can dang sure zip it downfield. Same with Winston.
I do think that D. Harris can fill that role some, and TQS is fast for his size. But they're both 4.48-ish /40 guys. Which isn't true burner speed, but should be enough to get downfield some to keep defenses honest.