Solving space puzzle, once again

I need to plant another apple tree in a pretty tight spot. I am going to have Antonovka on dwarf root stock, espaliered.
The area already has two romance cherries and a young espaliered apple tree as you can see on picture bellow. You can ignore all the plants there other than the trees mentioned, They will be gone in a month or so.

And another wider view:

What is not on the picture is 3’ diameter stamp to the left, at the end of concrete path. My idea was to build another espalier in parallel to the shed wall, perpendicular existing one like in T structure with new tree planted about 1-2’ behind the green post that is closer to the red barn. It will be about 4.5-5’ to the edge of the stump. My concerns:

  1. Stamp has some hard Polypore mushroom growing on it - can it affect my new tree?
  2. Concrete will be just 2-3’ away from new tree on one side. Will it affect root growing(this is the question for both trees I guess)?(don’t care about concrete)
    3)Will perpendicular existing espalier shade the new tree to a bad extent? ? What about cherry bush, it will shade some morning sun, can new tree tolerate it? Sun comes up where the red roof is, so it is a pretty sunny spot.
    Does it even make sense to try or it is too tight?
    And another, completely crazy idea… Can I plant a new tree on the same espalier structure like 3’ away from existing tree where garlic is growing now, but make their layers on a different height, for full length espaliered branches for each tree? Another option would be to build a parallel espalier 3’ from existing one, where the plastic bags are now. This will leave 3.5 ’ between new espalier and cherry bush trunks. I know, there is no good solution. But is there any?