Redoing his contract wouldn't really help that much in terms of trading him. The cap hit to the Cowboys is the same regardless. You can't redo contracts to avoid dead-money. The new team would only be responsible for his base salaries which are not guaranteed. If the new team is cap strapped, then he can sign a new deal that would allow them to defer the cap hit to later years. He wouldn't have to take less money for this to happen.
I didn't really think a team would go this route (trade for Romo), but after the Sam Bradford trade, I realize that anything is possible.