Valerie, I think maybe over 90% of plants have an association with mycorrhiza. I think the cabbage family is an exception. All
trees that I know of love the association because it's a good source of phosphorous in particular. (plus other micronutrients)
Apple trees are very adaptable. I don't see why a former bean field wouldn't work. I plant fruit trees in groves, not in lines like a orchard. The permanent mulch below allows for easy pruning and harvesting. The insectary plants are at the edges of the trees as the insects can easily fly the distance to the tree/fruit. I don't plant annual vegetables under fruit trees as they don't need, or often don't like, the extra nutrition. (Promotes aphid attacks among other things.) I would never try to move a nut tree. As far as I know, juglone is mostly a concern for black walnut trees - Juglans nigra. Some Coop. Ext.s have lists of plants that are hurt by juglone, but, if they're comprehensive, the plants that can grow well near the tree. (Try a good list of the juglone susceptible and tolerant plants from John and Lewis Jett of the West Virginia Extension Service)