Hi Charli.
Were it me, I would look to a food forest model. If there is a favourite fruit tree you like, perhaps build a guild around it, and try to include all the different plant actors on the scene, and have every trophic level occupied.
You could also do similarly with annuals, in a vegetable patch arrangement, but I would still choose a single plant or pairing of symbiotic or otherwise mutually beneficial plants and build a selection out from there.
So while you might not want to do this, or it may not be suitable for the climate, you could, for instance, do a mound of seeds containing corn, beans, and squash, colloquially and conventionally known as the Three Sisters, add some bee balm or other bee-friendly plant, and call it done, and on the small scale, with added supports, you might even be able to use the technique for sweet corn, summer squash, and fresh beans (the technique was developed to be neglected all season and harvested dry, all at once, and using winter squash, all for storage).
My tomato guild includes oregano as groundcover, basil as intermediate herbaceous plants, peppers interspaced evenly with the larger tomato plants, and of
course, tomatoes. The oregano and basil are scent distractors, confusing tomato pests that track by scent, and growing basil within nine to ten inches of a tomato plant can increase that plant's production by up to 20% (this stat is on my list of links to find for posting, as it seems to come up a bit). Peppers, as a plant between the sizes of tomatoes and basil, fits nicely in that in-between niche, and also benefits from other solanaceae, as they need the sun for growth, but also need dappled shade, which the tomatoes provide, to keep their fruit unburnt. I also like to add onion and/or garlic nearby, for more scent distraction, and carrot, which gets stunted by the tomato, but helps the tomato to grow. A perimeter of marigolds and mints are usually really good to keep out insect and rodent pest alike.
So if you wanted to go the espaliered tree route, I would go with something like
apple, pear, or stonefruit of whatever kind, and perhaps some cane berry bushes to either side, with an herbaceous berry at their feet, along with garlic chives. You could do rhubarb in the shady bit between cane berries and the shed, and it would serve to shade out the soil. Plus, rhubarb makes excellent pie, on its own, or to balance out really sweet berries.
You could do a tree, a couple of shrubs, some cane berries, some low-growing
perennial bushes, walking onions, vines,
wood chip mulch and inoculate with your favourite site-appropriate culinary
mushroom, whatever. Or literally almost all of these things together. Some wisteria can apparently host nitrogen-fixing bacteria, which make it a good choice for squeezing into tight spots.
But let us know your thoughts. I hope these ideas are of some use to you. Keep us posted, and good luck.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein