I agree. And Jennings is a very, very determined blocker (excellent if they kick to Henderson but more of an open question if the kick is the other way, as is more likely).
Signing Corbin is fine, but the world has moved on from when the Patriots lost almost all of their running backs in 2018 and had to sign players off the street.
Since then, Practice Squads have expanded and the rules on who can be part of them have relaxed. It would make a lot of sense to sign a player from another team's Practice Squad.
There are currently (on a quick count) 31 running backs on NFL practice squads. Seattle have three of them. Pretty much every team has its Lan Larison -- some training camp hero that the fans are in love with. I can't believe that there isn't at least one really good player out there.