Is an Executive Doctorate different from a typical PhD with respect to the level of assistance that is permitted on the dissertation?
Based on this article, I would guess the answer is: officially, no.  It seems quite unlikely to me that there is some other standard of intellectual honesty specifically set up for "Executive Doctoral" student, since it is such a new category.  

It certainly sounds to me like this person is asking you do an inappropriate amount of work toward their doctorate; doctoral students aren't expected to be completely isolated (much of my thesis was based on joint work), but asking you to rewrite seems like crossing a line.  It's up to you to decide what you want to do, and whether you feel comfortable with the work.  You could always contact the person's advisor, but you should be prepared for that to burn your bridge with this person.