Most Twins rentals have real value to a contender. Coulombe will have multiple suitors, as will Castro. Bader, being a great defensive player, is someone almost any team can use.
If the front office doesn't trade the good rentals, they need to go. Full stop. No, you're not going to light the world on fire with any of those player returns, but given how multiple teams will want all of them, the return ain't nothing.