It's one thing for the Cubs to unload Contreras just to reshuffle the deck chairs, but if a team out there really *wants* him and we can extract appropriate value, I'd definitely listen. So hard to move any other meaningful asset and get real value back: given limited control trading KB will likely make the Cubs worse, Cubs value Schwarber more than other teams, and Baez isn't going anywhere.
That said, as I've continued to think about the roster, I have wondered more and more about a Rizzo trade... he's probably good for 8 WAR the next two years, and will cost $32M, giving surplus value of basically $32M. If you trade Rizzo, you can move Schwarber to 1B, and then bring back Castellanos for LF. That "diversifies" the Cubs offense in some of the ways Theo would like to, Cubs get a little younger, add additional years of control to the roster, reshuffle the "leadership" voices, add some "intensity", and the salary difference between Rizzo and Castellanos shouldn't be so large so as to impact other moves.
So what does $32M surplus value get you? Well, Merrifield is under contract for 3 years at about $16M (after considering likely incentives). He's probably worth about 7.5 WAR over those 3 years, which comes out to $44M surplus value. $44M - $32M leaves $12M in surplus value to make up, which is basically a prospect in the top 100-150 range. Royals have a black hole at 1B, and if Rizzo plus a marginal prospect brings back Merrifield, that's worth considering, IMO. Especially if it triggers a Castellanos signing. Further, the Royals' farm system is even worse than the Cubs', meaning the prospect we send back would instantly qualify as one of their "top prospects."
Cubs then go:
C - Contreras/Caratini
1B - Schwarber
2B - Hoerner/Bote/Happ
SS - Baez
3B - Bryant
LF - Castellanos
CF - Merrifield
RF - Heyward
Cubs don't really lose financial flexibility in 2020 and likely gain some long-term, get younger, and address CF/leadoff in a market that otherwise has no good options. Contreras is still available to acquire pitching, if the right deal comes along.