Barkley gave them 1.650 rushing+receiving yards on a whopping 352 touches. If you extrapolate Breece Hall's season to a full one, you get 1.653 rushing+receiving yards on 240 touches. On the Jets offense, as a second-round pick. So imo the Giants could easily get someone like Bijan, Gibbs, or the RBs a tier below that and get similar production. Even a slight downgrade would be worth it if you can add important pieces in the trenches or elsewhere.
Very much agree though that the passing game is their biggest need. They should be hoping JSN makes it to their pick.
Ultimately, its about the total yards he generates. 1,650 is top 7 in the league and with one game less played than many ahead of him. Unless the Giants have a player in mind who can replicate that for less money, they will try to keep him. If they want to win they will need a WR to get them there.