I think that many (but not all) excavators have a personality where they do what they want rather than what the customer wants, even if they say otherwise. Not sure why, but that is my experience. Best advice that I can give is to find an excavator that already wants to do what you want, or build it yourself.
Most of them think they always know better than the land owner, IME. But, I found that if I insist enough, I can get them to do more of what I want. The problem is getting someone to even show up to work.
