First, I'm not sure MB can be traded without this team eating salary. So say it costs 4m, and what do you think Lester or Shields will cost? Add about 4m to that and you can guess why MB is not going to be traded. This team has no vision, unfortunately AA is here for another year, and I highly doubt a GM on the last year of his deal is going to look to rebuild a team that desperately needs to be rebuilt from the ground up. The way this team is constructed right now, it needs another 20-25m in payroll for it to have a chance next year. That's assuming JB doesn't decline a lot as most players in their mid 30s tend to do.
The biggest trade this team could make would be swapping front offices with another team.