Great garden. Here are some ideas: now, for the winter lettuce you can strew cornsalad seeds (great in autumn and early spring, but it overwinters, too) and matador variety of spinach (overwinters), or some winter chicory, or wintercress, and maybe chinese kale. In spring take care that some of the spinach and cornsalad create seeds and are blown around by wind or pluck the plant out when the seeds seem to ripen and place them where you'd like the cornsalads to grow in the autumn. For the shadow you can also use snakebean, new zealand variety of summer spinach, akebia chocolata (considered an invasive plant in Europe), passion flower (makes good fruits), or maybe raisin variety of grapevine, Chinese schisandra, kudzu plant (also considered an invasive plant, root used as thickener, but needs quite some preparation), maybe you can even plant goji berry plants (it creates a bush, but I've seen them hanging over a fence as more or less single branch as they thrive in full sun) and you can plant climbing beans next to the corn plant as it is their fertilizer, and spinach leaves phosphorus in the soil. Cornsalad thrives also under tomatoes if seeded in August. I guess artichokes would do well too (leaves are used as tea). Or you can plant some bamboo for bamboo shots and leaves as tea (it's invasive plant too).
And as for higher mountain ideas maybe you check Sepp Holzer.