Possibly. But think of it this way: even if you lose a hardiness zone in a microclimate with poor air drainage, you'll still be growing your fruit in zone 3b/4a conditions, and that's good enough for most temperate fruit trees. Many hardy varieties of fruit trees have been bred for short-season areas, and if I can grown apples, cherries (pie), and pears in northern Alberta, I think it's likely that you'll find suitable varieties for your comparatively more temperate climate.

The western exposure may be more problematic than the low spot, though: you might have to paint the trunks with a reflective paint so that the trees don't break winter dormancy too soon in warm spells. It probably won't be too much of an issue, though.

Grow your dwf trees above and terrace for others like bushes, and leafy greens down below? Since the late frost protection from being up and having better air circulation will work, now you have to battle the fungus. I assume you have a lot of dew late into the AM?