Moon, the elephant in the room that goes beyond any coaching changes or rebuild by trades or sudden development by one of the higher Sox MiLB players or extension of Betts is what can Sale/Price/Eovaldi do next year, and can Erod maintain his 2019 success.
Without those 3 earning their punishing contracts, the position players output won't matter any more than it did this year. The real problem is that the Red Sox won't know what those 3 can do at the earliest mid-February and more likely Memorial Day 2020, when it will be too late to make much of a difference.
Additionally, a #5/6 starter needs to be acquired who can outpitch the Johnson/Velazquez/Weber bunch. Porcello despite all the moaning and groaning filled a big slug of innings and won at about the same pace as the team did.
The starting pitching was considered the strength in Spring 2019 and faltered badly despite Erod's emergence. Shuffling Beni, JBJr,Betts, JDM, etc is not going to answer the question of the starters contribution. A good year by each of them will turn the Sox into competitors again. Poor results and it will be over by end of May.
An incoming GM, or internal promotion will be seriously challenged because they have the contracts to pay out, but do they have 1, 2, or 3 capable starters for the next few years ? Recency tells us do not count on Sale or Price and Eovaldi is iffy too for a full season.. Not good odds.