When I see Willson, I don't see catching or hitting. I see leadership. Unfortunately you can't measure that. But when you have a guy so committed to his team as Contreras, I think you have to find a spot for him, 1B, DH, LF if you trade Happ. But the guy bleeds Cubbie Blue. He's an extra coach. I think his spirit and drive especially as he influences the younger players Hoyer will regret he didn't consider.
On the topic of "non-quantifiable", hard to think of anything more non-quantifiable than "leader" and "bleed Cubbie blue".
If you want to keep Contreras around as a DH, you have to pay him accordingly. How much is a DH whose OPS over the last three seasons is about .790 worth, and would Contreras feel good about signing for that?