There are consultancies like Hay/MSL who advise Boards on salaries, up to and including CEO's and Directors. There is also a quarterly salary and benefits survey that gets trotted around - you get a copy if you participate in the survey.
I would think that Dixon's package would have some relationship to this type of benchmark - it would be in the minutes of the remuneration committee meetings.
The actual terms of his contract would depend on how good a law firm he uses to negotiate it. The trend in the U.S. is to have an employment contract and a back to back severance contract as well. The severance contract usually has a number of "triggers", like takeover/change of control, termination as an employee, mutual agreement etc. etc. It also would have vesting rights clauses regarding options and all that jazz.
The trouble with changing an organisation's culture is that everyone is for change when it involves someone else, and against it when it involves themselves. You either do change quick and dirty, like a variety of U.S. airlines in bankruptcy, or you do it slow and cleanly with consultation, voluntary redundancy programs yadda yadda. Quick and clean is an impossibility and slow and dirty is awfully suboptimal. Guess which method Dixon is using?