Some of the FO's thinking with Lester was their philosophy, at the time, of not signing pitchers into their 30s to long term contracts. I'm not sure that Lester would have come back to the Sox even if they had given him a second offer. I agree, though, that it wouldn't have hurt.
I have never wanted to sign Mookie to that kind of contract, so in that regard, I'm glad the Sox didn't give him another offer.