Lupines are a great N fixer to use as well. I have lupines growing that are descendants of seed i brought back from Sepp Holzers farm in Austria. Way cool,hey.? Definitely a mix of many suport species contibutes to a healthy soil ecosystem and nutrient cycling.
Eleagnus ssp are great to include if you have the well draining soil they require. I tried for years unsuccessfully to establish russian olive, autumn olive, and wolfberry on my heavy clay soil, which was badly farmed for a century. It came with a severe hard pan, low organic matter, a severe ubiquitous quack grass (Aka couch grass) infestation, and very poor drainage.
The areas where i have been adding organic matter ( bags of leaves collected in town, cardboard, scrap lumber, rotten logs, chop and drop from biomass plantings,comfrey, etc) for 5 years now can now support some spp that require ok drainage. The best result so far, however, is planting eleagnus ssp, caragana , wild blue indigo, and honey locust,etc on the hugel beds i put in.
Various clovers, alfalfa, vetches, etc are doing well all over the place on my farm and are much appreciated. Comfrey is not a N fixer, but it is a miracle plant in so many other ways.
Blk locust didn't grow fast for the first several yrs on the hard pan clay, but it did at least survive and grow slowly and my older bkl locust plantings are now growing well. This is a major reason that i love BL so much.
Goumi, unfortunately, won't grow this far north. The invasiveness of russian and autumn olive is generally highly exaggerated. These are pioneer species whose job it is to heal damaged/ disturbed land. Once they have done that job, they gradually die off as other forrest ssp take over if nature is allowed to follow natural succession.
It is when humans ( and in some areas with really tough growing confitions such as alkaline soil, dry, desert areas, etc) interfere with the natural tendency for most land to gradually return to forrest that eleagnus ssp can take over. When humans keep disturbing the land with mowing road sides, plowing, over grazing, spraying herbicides, construction/expansion of buildings,etc, it freezes natural succession at the state where eleagnus and other pioneers are needed to heal things, so they step up to do their job.
They just aren't a threat to the local wild ecosystems where i live, which by the way, are already heavily " contaminated " with a wide range of introduced ssp that have happily naturalized themselves and most people don't even realize that they aren't native. Think dandelion, apple, plantain, earthworms,etc.