Let's remember, that ESPN has a long successful run with promoting their products and shows. During that run, they have negotiated with many, many high profile atheletes. While many liked 'Fish', he would not be successful telling ESPN what to do - as evidenced by the goings on.
If you want to be a 'public' figure, you generally have to do it on their terms. Look at Jimmy Johnson and the Fox gig. He wanted to do it from Florida, as he had done on HBO previously. Fox said no, in studio and other work. Guess who won.
If you want the 'money', you have to dance to the tune.
Tex