Has anything been explored other than irrigating the water directly to the orchards or gardens? I saw in another post that storing the water or filtering through a reed bed is not recommended. Would a second stage filter something like a biofilter used in an aquaponics system provide adequate filtration to clean the water enough to add it to the grey water going to a constructed wetlands?
If you have the water tested first so you're confident no pathogens are coming through the tank, you could probably take the water direct to a constructed wetlands as the water exiting the tank is generally cleaner than grey water. But I would want to put some failsafe mechanism in place between the two. IF your tank were to block (eg. organic material that's too fine gets into the mix and clogs the filters), then sorting the blockage without diverting the water going to the wetlands wouldn't be advisable. You'd want some sort of other soakaway until the system is stable and working again.
At the end of the day, keeping everything aerobic (soil-based) is the surest guarantee your waste is being treated safely and thoroughly. Taking it into an anaerobic system (wetlands) does make potential problems more likely.