Yes - extremely common in Britain on waste ground, neglected allotments, etc. Now you have your eye in you'll see them all over the place.

I guess the problem is I never met a plant I didn't like. Maybe it's because the conditions in which some of them developed their own particular characteristics to cope, and even to thrive, are envisioned and appreciated. When I think of the relentless difficult desert conditions that cacti, agaves and succulents and that whole family of plants endure they become a metaphor of this world with lessons to teach as well as their own type of tenacious beauty to share. Cacti, like some of us, manage to survive and grow in the harshest of climates, and while prickly on the surface they strive in their own way to show us beauty in the design of those very prickles and thorns and in the graceful shapes of their forms. Their true colors and magnanimous inner softness emerge in spring, or whenever the conditions are not so harsh, as they open up their blossoms to display their sweetly scented nature that lives within, as if to say "Love us for what we are -- since we couldn't have survived otherwise -- and we will show you our inner loveliness as well."

assimilant partitioning or put another way the first child gets the lion's share of what's available

Overwintering something in a container is much easier in a zone 7b than it would be in colder zones. Zone 7 soils do not freeze to any significant degree and most plants will tolerate the colder air temps as well. Winter protection is generally not a requirement unless growing only marginally hardy plants. If you want to grow something year round in a container, pick something that will look good year round. Anything can be grown in a container provided the container is sized correctly and other concerns re: container gardening are properly addressed - proper soil mix, fertilizing and watering, repotting and/or root pruning. A mixed container generally has more interest than a single plant type, so a dwarf evergreen shrub, a small ornamental grass and one or more flowering perennials is a good basis from which to start. And you can mix this up if you wish, subbing a deciduous flowering shrub as the centerpiece (or a dwarf conifer) and adding evergreen perennials like heuchera, hellebores, euphorbias, bergenias, etc. Fine Gardening typically has a great presentation on mixed containers, both in their magazine (seasonally) as well as many of their online articles that are good for inspiration. Keep in mind the three basic elements - "thriller" (centerpiece plant), "filler" (fluffy/full middle ground plants) and "spillers" (cascading plants/grasses or groundcovers) and it's hard to go wrong :-) btw, I'd suggest you spend some time visiting the Container Gardening forum to bone up on potting soils and fertilizing needs and other CG requirements that are very specific to this topic. It will be hugely helpful and informative.