I think I'm one of the younger posters here but I'm still old enough to remember Bethel Johnson as the #4 WR behind Branch/Givens/Brown scoring a 40 yard touchdown against TEN in the divisional round in a game we went on to win by only 3 points on our path to a championship. Even depth players can make a play that means the difference between winning and losing a playoff game.
Kyle Williams has been playing a lot since the Boutte injury but even before that he was getting 10-15 snaps each week and he's been very bad, consistently looking out of place and not in synch with the rest of the offense. We're 9-2 and going to be in the playoffs. It's very possible that one or two plays made/not made on those 10 snaps a game can be the difference for us. I'm not at all ready to give up on his career yet, but I don't feel at all comfortable putting him out there in big situations and IMO we're too good this year to be playing guys clearly not ready yet just for developmental purposes. It's one thing to prioritize playing young guys who might F up here and there but make their fair share of plays, but throwing guys out there who look clueless for be big regular season games and PLAYOFF games should be out of the question right now IMO. Not when you're this good. Let the guys not at all ready to play yet by this point have a redshirt year the rest of the way.
If they think Cooks can give them more than they're getting on those 10-15 snap a games, I say they should go for it. He has familiarity in the offense and his route tree/physical profile would seem to fit well for whatever it is they're trying to get Williams to do on the snaps he's out there. He'd probably even be a good mentor for him.