**IF** the "must-get-under-any-lux-tax-threshold" premise is true, then I think the status quo is the best option. Keep Bryant and Contreras and Baez and Schwarber. Keep Chatwood.
The Cubs have won a bunch of games with the existing cast, and almost got in last year too. If some guys play better and improve, and they get some luck, and some guys develop somehow, they might get into the playoffs with the status-quo roster.
I think it's much less likely that they compete for the 2020 playoffs if selling Bryant or Contreras for money-relief and futures prospects.
Plus "status-quo" isn't really a thing. Even if they don't trade any of the big 4, the roster will still be significantly adjusted from what they opened with last year.
Plus even if guys are the same, that doesn't mean they'll play the same. Maybe Schwarber will be better. Maybe Hoerner will be a whole lot different than Russell. Maybe Happ will be different and better. Maybe Q won't be 4.68-ERA bad again? Maybe the bullpen won't lose so many saves? Maybe Kimbrel won't be the worst pitcher in the league?
You can bring the same core personnel back, "status quo", but the season won't play out the same.
I don't accept any of the supposed givens (such as staying under the luxury tax threshold). They may be true, or they may not. Who knows? Only Theo and his closest associates, I'm guessing. I'm inclined to think that others are speculating, even if it's somewhat informed speculation.
I do not expect the Cubs to stand pat over the winter. They won't trade Bryant (or Contreras) just to trade him. If they do not get a sufficiently attractive offer (whatever they believe that to be), he'll be back. But it will be a different team, to some extent.
And if Darvish can be the pitcher for the full season he was for the second half (or something close), that would be a huge upgrade, even though Lester is likely to continue to decline. I think it's credible that Schwarber really did turn a corner and that he could repeat his second half, and that 2B and CF are reasonably likely to be better than last year (a relatively low bar).
Big questions to me are whether the Cubs can strengthen their rotation after Darvish and Hendricks, how much of an improvement they can get at CF and 2B, how much they can improve their bullpen around the edges, and IF they trade Bryant, who will play 3B.