My logic against signing Keuchel:
If it is a multi year deal, you are giving up the chance to sign Cole/Madbum/etc, since we already have Gio/Kopech/Lopez/Cease (I am fine giving lopez until at least Rodon gets back)
If it is a single year deal, you are spending money that may be more useful this winter to chase a playoff berth that IMO opinion is still out of reach for us. Also, I doubt he wants to take a rebound contract for an AL team that has very little playoffs chance and plays in a hitter friendly park.
I would still be happy if they sign him, just so I don't have to watch one of Banuelos or Covey anymore. But I don't think it is a good move.