I've been making plans very similar to yours. Here are some of my ideas:
Lay fallen
wood above and below wild plum trees and other edibles. Cover it with leaves and the dark soil scraped out from under big trees. Then dig a trench above it and put that dirt on top of what you already have. My thought is you slow down the water and let it soak in while feeding the wild tree so it has better fruit.
You could also graft plum or peach or whatever works on that base tree to get better tasting fruit. If you have a lot of these, maybe the deer and turkey won't eat all the fruit before you get to it. They left my peach trees alone and I get quite a bit of fruit off the wild trees even though there are a lot of deer and turkey here.
That could be because there is a ton of buckbrush covered in berries and sumac everywhere. Maybe they prefer that.
I've also harvested Chanterelle
mushrooms, blackberries and what I believe are huckleberries. Those are all located far from any buildings in an area heavily utilized by the deer and turkey. (I see them nearly every time I go out to the blackberry patch.)
Found what I believe to be service berry trees (aka June berries), but I forgot to check them at the right time. My plan is to borrow some of the decomposing wood and dark soil from under trees near the wild fruit trees and shovel some manure if any is handy, and chop/drop some greenery around those fruit trees to naturally fertilize them to produce better.
Another idea is to find an area where a tree fell and is decomposing. Scatter a mix of seeds near that trunk (or even just fallen branches) and see what wants to grow there. Then plant more of what took off or just let it spread naturally.
Winged elm seems to be a pioneer species in Oklahoma. Wherever branches or tree trunks lay decomposing, winged elm pop up around them. So another idea is to plant pits and seeds from various fruit trees (peach, plum, apricot,
apple, pear, fig, etc.) in among the winged elm. They may provide some protection from deer while the trees get established.
I know that fruit doesn't breed true, but if it isn't tasty to eat off the tree I would make jelly out of it. Or possibly graft other varieties onto it. If a tree produces well, I could consider fencing it off later.
Where water runs down a hill, wild plums and winged elm get established. Use the first idea (slow down the water and increase fertility) multiple times as that water runs towards the
pond (which overflows and causes erosion -- so there is clearly more than
enough water to divert some of it).
Plant guilds on each mound: 2 fruit or nut trees, 1 nitrogen fixer, 4 berry bushes (gooseberry, black current, red current, blackberry, raspberry etc.) between the trees and 30 perennials (TexasBoys comfrey, herbs, garlic, chives, rhubarb, sweet potatoes) around the trees and bushes.
Modify the quantity if necessary, but I'll try for that and put in several of these between 3 existing wild plum trees and the pond that water is running into.