I don't think any Class C mfg puts door side arm rests on. For the most part I have always adjusted my seat/steering wheel so it make the door more comfortable then I alternate from door arm rest to window or put a hoodie on the door...but that is on an E450.
PLEASE do not send questions via Private Message, my inbox fills up too quickly. Post questions in the forum as a new thread so that other users can benefit from the answers. Use Private Messages for sensitive information only (VIN, Contact info or things you do not want the public to see).