Great ideas Martin,
a couple of suggestions
planting clover with current crops to add N, supply flowers to help pollinators.As your crop grows it should crowd out the clover.
increase the diversity of plantings, it seems logical that plants of the same variety are going to have the same nutrient requirements, therefore if you vary your plantings you get less competition and greater production from the same area.
comfrey & or aloe vera as a mulch/compost crop
increase the number of productive horizons you are using like your use of ground covers with bananas, how many different layers can you get in your garden area without too much shading?
e.g. putting in paw paws along fence lines, passionfruit on fences (with bird netting).
deep ripping along contours in areas you don't have under veggies (reduces runoff)
solar pump on lower dam to recharge upper dam (if you need it).
I was also thinking nasturtiums might be good with bananas to help with nematodes - haven't tried it yet.
keep up the great work
Rob