2023 starting lineup: 1B Casas, 2B Story, 3B Devers.
Whoever is running things needs to find a new catcher and new shortstop who are glove-first professionals; guys like that shouldn't be too expensive, but should be priorities in lending stability to any rebuild.
Where the Sox need to spend big in bucks or prospects is on the outfield; they need at least one, and probably two, legitimate big league borderline stars who can hit and hit with power. They have none close to being ready in the minors. The line-up has already lost the pop once provided by JD and Bogey, and their production needs to be replaced, not to mention the missing longball void still open since Schwarber and Renfroe left.
The most costly addition will come on the mound, where Boston needs an ace. People can argue a non-contender should spread out its investments and build depth, but it all begins on the hill in the middle of the diamond. No one can turn around a staff or a team faster than a #1 who consistently provides quality starts every five days for six months.