Nick, If you are still interested in getting ideas, I have one for you. How about sea buckthorn (Hippophae rhamnoides) as a crop? It is an incredibly valuable fruiting shrub or small tree--the berries are chock-full of nutrients, (about and both berries and leaves are used in herbal medicines and foods. Best of all it tolerates places and conditions that a lot of plants can't. It loves any soil--including sand and gravel; tolerates wind, sea and salt (grows well along shorelines) and is hardy in USDA zones 2-9. Best of all you can get a huge crop from these shrubs in as little as 3 years. This is a widely used plant in eastern Europe and Asia, but only just beginning to catch on here in the USA.
Here is what the National
Gardening Association says about it...
"Seaberries are easy to grow and require little space. Because male and female flowers grow on separate plants, you need at least one of each sex to produce fruit. Flowers are pollinated mostly by wind, so space plants closely: 6 to 8 feet apart in rows, or 3 feet apart as a hedge. One male (distinguished by its larger flower buds) can pollinate five or six females.
Plant seaberries in spring in full sun. They grow in most soils, even sand or gravel, tolerate both seashore and road salt, and withstand drought well. They seem to do best in a well-drained soil (pH between 5.5 and 7.5). A thick organic mulch, renewed each spring with compost or manure,
should supply all the other nutrients they need and protect the shallow
roots. Seaberries grow quickly and usually bear their first fruits two to three years after planting. Some varieties produce 30 to 50 pounds of fruit per shrub annually, but it may take several years to reach maximum production.
Seaberries need little pruning, unless you want to train them into bushy shrubs or shapely small trees. From time to time, cut out damaged or unproductive branches. Prune in fall after harvesting the berries in late summer. The plants resist most diseases and insects, so spraying is seldom necessary."
Also check out its stats on Plants For a Future's database...
http://www.pfaf.org/user/Plant.aspx?LatinName=Hippophae+rhamnoides