I know people who feed outside the enclosure and swear by it. I find it easier for me to feed in the enclosure. I really don't think they will associate your opening the door and seeing your hand with food. You have to open the enclosure and put your hand in to take the snake out to bring it to the feeding box. If they are going to associate your hands with food, they will nail you taking them out of the enclosure.
I have a 13' burm and a baby burm and retic now. I don't find it an appealing idea to have to have to move a 100+ pound snake before feeding and more so after feeding. Just my opinion.