This should be worth it to both clubs. Keep the Big Four, Casas and Duran. Abreu is blocking Anthony, and is the top trade chip by default.
I'm also not trading Arias this winter -- not with the uncertainty of Mayer's durability the past two seasons. One of them may be the shortstop of future Boston core teams, but Arias is noted for his glove, while Mayer's potential is more with his elite bat.
Plus, Trevor Story is under contract for three more years, and the next time he goes on the IL we should get to see and evaluate Mayer on the big league stage.
Trade for Crochet and sign Manaea, a starter who worked well with Andrew Bailey in San Fran in 2023. Sign Higashioka to partner with Wong. Higgie has a productive righty bat, hitting 17 homers last season.
Spend the rest of the budget on the bullpen.