You could also pretend hes taking a pay cut cause he wants to stay in Boston to help them win? idk but I understand what you're saying but I agree with the first commenter, it is very frustrating seeing 5star players sit in FA and not even sign a cheap contract somewhere or a 1 year 7m deal in the KHL somewhere so it's not perfect but just use a little imagination and it makes the situation a bit better
Also I know its extra work but if it bothers you why not just edit the contract in Comish mode to something you would think is more fair? Sure its more work but if it makes the game playable for you then it's probably worth the extra effort.