I think the best time to trade Yoshida may be this summer, but he will have to be showing he can hit near .800 to make a difference over trading him, this winter. Either way, we will have to pay more than half of his remaining contract, and maybe 70-80%.
Finding a taker is the toughest task. Taking on a big or bigger contract might work, if we get back an overpaid pitcher who still has some hopes of being helpful. The problem with that is, when a team is looking to dump a grossly overpaid player who still has some value, they usually want a full dump. They are not looking to just save a couple million a year.
To me, STL might be our best hope, and getting Arenado back to play 1B (NOT !B!!!!) would greatly improve our defense and our offense vs LHPs. He is clearly in decline, and may drop off a cliff, at any moment, but Yoshida at DH for us, forces Casas and Devers to play a position. Plus, I'm not sure Yoshida is any better than Anthony, Campbell and others who are looking for a position to play. Also, Refsnyder hits LHPs better than anyone on the team, right now, and his best position is a DH platoon.
I'd offer STL some secondary prospects, and maybe even Crawford, if we add another SP'er like Burnes, Manaea, Flaherty or Pivetta. Arendao is owed more, but COL pays $5M x 2 years of his deal and his third year is $15M vs Yoshida's $18M. Just get it done!
I'd try to keep Arias, but if the plan is to keep Mayer and Romero, I'd be okay with making Arias part of the deal. We might offer Bleis, Cespedes, Romero or JH Garcia, instead. I'd hesitate to trade 2 of these guys, especially if one is Arias, but I might offer two from the others, with one being Romero.
I'm not sure that gets it done. We might have to add Fitts, Dobbins or Sandlin to the list of who STL can take.