Mendick + A bullpen arm around $5mil/yr > Yolmer at his cost.
Yolmer should be gone unless he's willing to sign real cheap.
Leury can stay as a super utility player.
Consider the 2017 draft as an example of why 1 or 2 spots can make a difference.
Pick 9: Keston Hiura MIL: having a great rookie season
Pick 10: Jo Adell LAA: one of the top prospects in baseball.
Pick 11: Jake Burger
My guess is Mercedes gets added to the 40 man prior to rule 5 in December. Especially with the amount of players like Skole on the 40 man who can easily be removed.
I would think an AL botton feeder team like Baltimore or Detroit would take him in the rule 5 and see if he can be a DH. No reason the Sox shouldn't give him a shot.