How to remove the email field when placing the order?

If you are already in the system ready to customize, the easiest way is at the template level order - using javascript to make the input field invisible email, and at the time of entering phone enter in the field email the email type telephonetelephone - because no email order cannot be created. Look at the code of the components of the quick order of the marketplace - they are all something to substitute in as email.

store settings - order properties